Intel 80X86 ASSEMBLY LANGUAGE OPCODES
Notations and Format used in this Document
AAA - Ascii Adjust for Addition
AAD - Ascii Adjust for Division
AAM - Ascii Adjust for Multiplication
AAS - Ascii Adjust for Subtraction
ADC - Add With Carry
ADD - Arithmetic Addition
AND - Logical And
ARPL - Adjusted Requested Privilege Level of Selector
BOUND - Array Index Bound Check
BSF - Bit Scan Forward
BSR - Bit Scan Reverse
BSWAP - Byte Swap
BT - Bit Test
BTC - Bit Test with Compliment
BTR - Bit Test with Reset
BTS - Bit Test and Set
CALL - Procedure Call
CBW - Convert Byte to Word
CDQ - Convert Double to Quad
CLC - Clear Carry
CLD - Clear Direction Flag
CLI - Clear Interrupt Flag
CLTS - Clear Task Switched Flag
CMC - Complement Carry Flag
CMP - Compare
CMPS - Compare String
CMPXCHG - Compare and Exchange
CWD - Convert Word to Doubleword
CWDE - Convert Word to Extended Doubleword
DAA - Decimal Adjust for Addition
DAS - Decimal Adjust for Subtraction
DEC - Decrement
DIV - Divide
ENTER - Make Stack Frame
ESC - Escape
Floating point instuctions - no descriptions
HLT - Halt CPU
IDIV - Signed Integer Division
IMUL - Signed Multiply
IN - Input Byte or Word From Port
INC - Increment
INS - Input String from Port
INT - Interrupt
INTO - Interrupt on Overflow
INVD - Invalidate Cache
INVLPG - Invalidate Translation Look-Aside Buffer Entry
IRET/IRETD - Interrupt Return
JA/JNBE - Jump Above / Jump Not Below or Equal
JAE/JNB - Jump Above or Equal / Jump on Not Below
JB/JNAE - Jump Below / Jump Not Above or Equal
JBE/JNA - Jump Below or Equal / Jump Not Above
JC - Jump on Carry
JCXZ/JECXZ - Jump if Register (E)CX is Zero
JE/JZ - Jump Equal / Jump Zero
JG/JNLE - Jump Greater / Jump Not Less or Equal
JGE/JNL - Jump Greater or Equal / Jump Not Less
JL/JNGE - Jump Less / Jump Not Greater or Equal
JLE/JNG - Jump Less or Equal / Jump Not Greater
JMP - Unconditional Jump
JNC - Jump Not Carry
JNE/JNZ - Jump Not Equal / Jump Not Zero
JNO - Jump Not Overflow
JNS - Jump Not Signed
JNP/JPO - Jump Not Parity / Jump Parity Odd
JO - Jump on Overflow
JP/JPE - Jump on Parity / Jump on Parity Even
JS - Jump Signed
LAHF - Load Register AH From Flags
LAR - Load Access Rights
LDS - Load Pointer Using DS
LEA - Load Effective Address
LEAVE - Restore Stack for Procedure Exit
LES - Load Pointer Using ES
LFS - Load Pointer Using FS
LGDT - Load Global Descriptor Table
LIDT - Load Interrupt Descriptor Table
LGS - Load Pointer Using GS
LLDT - Load Local Descriptor Table
LMSW - Load Machine Status Word
LOCK - Lock Bus
LODS - Load String
LOOP - Decrement CX and Loop if CX Not Zero
LOOPE/LOOPZ - Loop While Equal / Loop While Zero
LOOPNZ/LOOPNE - Loop While Not Zero / Loop While Not Equal
LSL - Load Segment Limit
LSS - Load Pointer Using SS
LTR - Load Task Register
MOV - Move Byte or Word
MOVS - Move String
MOVSX - Move with Sign Extend
MOVZX - Move with Zero Extend
MUL - Unsigned Multiply
NEG - Two's Complement Negation
NOP - No Operation
NOT - One's Compliment Negation
OR - Inclusive Logical OR
OUT - Output Data to Port
OUTS - Output String to Port
POP - Pop Word off Stack
POPA/POPAD - Pop All Registers onto Stack
POPF/POPFD - Pop Flags off Stack
PUSH - Push Word onto Stack
PUSHA/PUSHAD - Push All Registers onto Stack
PUSHF/PUSHFD - Push Flags onto Stack
RCL - Rotate Through Carry Left
RCR - Rotate Through Carry Right
REP - Repeat String Operation
REPE/REPZ - Repeat Equal / Repeat Zero
REPNE/REPNZ - Repeat Not Equal / Repeat Not Zero
RET/RETF - Return From Procedure
ROL - Rotate Left
ROR - Rotate Right
SAHF - Store AH Register into FLAGS
SAL/SHL - Shift Arithmetic Left / Shift Logical Left
SAR - Shift Arithmetic Right
SBB - Subtract with Borrow
SCAS - Scan String
SETAE/SETNB - Set if Above or Equal / Set if Not Below
SETB/SETNAE - Set if Below / Set if Not Above or Equal
SETBE/SETNA - Set if Below or Equal / Set if Not Above
SETE/SETZ - Set if Equal / Set if Zero
SETNE/SETNZ - Set if Not Equal / Set if Not Zero
SETL/SETNGE - Set if Less / Set if Not Greater or Equal
SETGE/SETNL - Set if Greater or Equal / Set if Not Less
SETLE/SETNG - Set if Less or Equal / Set if Not greater or Equal
SETG/SETNLE - Set if Greater / Set if Not Less or Equal
SETS - Set if Signed
SETNS - Set if Not Signed
SETC - Set if Carry
SETNC - Set if Not Carry
SETO - Set if Overflow
SETNO - Set if Not Overflow
SETP/SETPE - Set if Parity / Set if Parity Even
SETNP/SETPO - Set if No Parity / Set if Parity Odd
SGDT - Store Global Descriptor Table
SIDT - Store Interrupt Descriptor Table
SHR - Shift Logical Right
SHLD/SHRD - Double Precision Shift
SLDT - Store Local Descriptor Table
SMSW - Store Machine Status Word
STC - Set Carry
STD - Set Direction Flag
STI - Set Interrupt Flag
STOS - Store String
STR - Store Task Register
SUB - Subtract
TEST - Test For Bit Pattern
VERR - Verify Read
VERW - Verify Write
WAIT/FWAIT - Event Wait
WBINVD - Write-Back and Invalidate Cache
XCHG - Exchange
XLAT/XLATB - Translate
XOR - Exclusive OR
Notations and Format used in this Document
Notation
--------
OP Instruction OpCode
XX Additional Code bytes
s Sign Bit -- E - Sign-extend 8-bit immediate data
N - Non
w Word/byte Bit -- W - 16-bit operanrs
B - 8-bit operanrs
len Instruction length
MNEMONICS Instruction syntax
flags oditszapc
||||||||+- Carry flag
|||||||+-- Parity flag
||||||+--- Auxiliary flag
|||||+---- Zero flag
||||+----- Sign flag
|||+------ Trap flag
||+------- Interrupt flag
|+-------- Direction flag
+--------- Overflow flag
mr = Addressing mode Byte = MODRM(mod-reg-r/m)
/0~7 = 2nd or 3rd Opcode (MODRM bits 5,4,3 from reg field)
d0 d1 = Displacement [Low-byte High-byte]
i0 i1 = Immediate word value
o0 o1 = Offset value
s0 s1 = Segment value
r0 = Relative Short Displacement to label 'sl' (-128/+127 bytes)
r0 r1 = Relative Long Displacement to label 'll' (-32768/+32767 bytes)
Mnemonic Notation
-----------------
mb=memory byte rb=register byte rmb=register or memory byte
mw=memory word rw=register word rmw=register or memory word
md=memory double word rd=register double word
mq=memory quad word
ib=immediate byte mwr=memory word real
iw=immediate word mdr=memory double word real
mqr=memory quad word real
mtr=memory ten byte real
sl = Short label np = near pointer
ll = Long label fp = far pointer
cr=control register dr=debug register tr=test register
Instruction General Format
+------+ +------+ +------+ +------+ +------+
|PreFix| |OpCode| |MODRM | |Disp | |Imm |
+------+ +------+ +------+ +------+ +------+
AAA - Ascii Adjust for Addition
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| AAA | 37 | | 1 | ------a-c |
+---------------------------+-------------------+----+-----+-----------+
Usage: AAA
Modifies flags: AF CF (OF,PF,SF,ZF undefined)
Changes contents of AL to valid unpacked decimal. The high order
nibble is zeroed.
AAD - Ascii Adjust for Division
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| AAD | D5 0A | | 2 | ----sz-p- |
+---------------------------+-------------------+----+-----+-----------+
Usage: AAD
Modifies flags: SF ZF PF (AF,CF,OF undefined)
Used before dividing unpacked decimal numbers. Multiplies AH by
10 and the adds result into AL. Sets AH to zero. This instruction
is also known to have an undocumented behavior.
AAM - Ascii Adjust for Multiplication
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| AAM | D4 0A | | 2 | ----sz-p- |
+---------------------------+-------------------+----+-----+-----------+
Usage: AAM
Modifies flags: PF SF ZF (AF,CF,OF undefined)
Used after multiplication of two unpacked decimal numbers, this
instruction adjusts an unpacked decimal number. The high order
nibble of each byte must be zeroed before using this instruction.
This instruction is also known to have an undocumented behavior.
AAS - Ascii Adjust for Subtraction
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| AAS | 3F | | 1 | ------a-c |
+---------------------------+-------------------+----+-----+-----------+
Usage: AAS
Modifies flags: AF CF (OF,PF,SF,ZF undefined)
Corrects result of a previous unpacked decimal subtraction in AL.
High order nibble is zeroed.
ADC - Add With Carry
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| ADC AL,ib | 14 i0 | B | 2 | o---szapc |
| ADC AX,iw | 15 i0 i1 | W | 3 | o---szapc |
| ADC rb,rmb | 12 mr d0 d1 | B | 2~4 | o---szapc |
| ADC rw,rmw | 13 mr d0 d1 | W | 2~4 | o---szapc |
| ADC rmb,ib | 80 /2 d0 d1 i0 | NB | 3~5 | o---szapc |
| ADC rmw,iw | 81 /2 d0 d1 i0 i1 | NW | 4~6 | o---szapc |
| ADC rmw,ib | 83 /2 d0 d1 i0 | EW | 3~5 | o---szapc |
| ADC rmb,rb | 10 mr d0 d1 | B | 2~4 | o---szapc |
| ADC rmw,rw | 11 mr d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: ADC dest,src
Modifies flags: AF CF OF SF PF ZF
Sums two binary operands placing the result in the destination.
If CF is set, a 1 is added to the destination.
ADD - Arithmetic Addition
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| ADD AL,ib | 04 i0 | B | 2 | o---szapc |
| ADD AX,iw | 05 i0 i1 | W | 3 | o---szapc |
| ADD rb,rmb | 02 mr d0 d1 | B | 2~4 | o---szapc |
| ADD rw,rmw | 03 mr d0 d1 | W | 2~4 | o---szapc |
| ADD rmb,ib | 80 /0 d0 d1 i0 | NB | 3~5 | o---szapc |
| ADD rmw,iw | 81 /0 d0 d1 i0 i1 | NW | 4~6 | o---szapc |
| ADD rmw,ib | 83 /0 d0 d1 i0 | EW | 3~5 | o---szapc |
| ADD rmb,rb | 00 mr d0 d1 | B | 2~4 | o---szapc |
| ADD rmw,rw | 01 mr d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: ADD dest,src
Modifies flags: AF CF OF PF SF ZF
Adds "src" to "dest" and replacing the original contents of "dest".
Both operands are binary.
AND - Logical And
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| AND AL,ib | 24 i0 | B | 2 | 0---sz-p0 |
| AND AX,iw | 25 i0 i1 | W | 3 | 0---sz-p0 |
| AND rb,rmb | 22 mr d0 d1 | B | 2~4 | 0---sz-p0 |
| AND rw,rmw | 23 mr d0 d1 | W | 2~4 | 0---sz-p0 |
| AND rmb,ib | 80 /4 d0 d1 i0 | NB | 3~5 | 0---sz-p0 |
| AND rmw,iw | 81 /4 d0 d1 i0 i1 | NW | 4~6 | 0---sz-p0 |
| AND rmw,ib | 83 /4 d0 d1 i0 | EW | 3~5 | 0---sz-p0 |
| AND rmb,rb | 20 mr d0 d1 | B | 2~4 | 0---sz-p0 |
| AND rmw,rw | 21 mr d0 d1 | W | 2~4 | 0---sz-p0 |
+---------------------------+-------------------+----+-----+-----------+
Usage: AND dest,src
Modifies flags: CF OF PF SF ZF (AF undefined)
Performs a logical AND of the two operands replacing the destination
with the result.
ARPL - Adjusted Requested Privilege Level of Selector
(286+ protected mode)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| ARPL rmw,rw [286] | 63 mr d0 d1 | | 2~4 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: ARPL dest,src
Modifies flags: ZF
Compares the RPL bits of "dest" against "src". If the RPL bits
of "dest" are less than "src", the destination RPL bits are set
equal to the source RPL bits and the Zero Flag is set. Otherwise
the Zero Flag is cleared.
BOUND - Array Index Bound Check (80188+)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BOUND rw,rmw [186] | 62 mr d0 d1 | | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: BOUND src,limit
Modifies flags: None
Array index in source register is checked against upper and lower
bounds in memory source. The first word located at "limit" is
the lower boundary and the word at "limit+2" is the upper array bound.
Interrupt 5 occurs if the source value is less than or higher than
the source.
BSF - Bit Scan Forward (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BSF rw,rmw [386] | 0F BC mr d0 d1 | | 3~5 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: BSF dest,src
Modifies flags: ZF
Scans source operand for first bit set. Sets ZF if a bit is found
set and loads the destination with an index to first set bit. Clears
ZF is no bits are found set. BSF scans forward across bit pattern
(0-n) while BSR scans in reverse (n-0).
BSR - Bit Scan Reverse (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BSR rw,rmw [386] | 0F BD mr d0 d1 | | 3~5 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: BSR dest,src
Modifies flags: ZF
Scans source operand for first bit set. Sets ZF if a bit is found
set and loads the destination with an index to first set bit. Clears
ZF is no bits are found set. BSF scans forward across bit pattern
(0-n) while BSR scans in reverse (n-0).
BSWAP - Byte Swap (486+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BSWAP eax [486] | 0F C8 | | 2 | --------- |
| BSWAP ecx [486] | 0F C9 | | 2 | --------- |
| BSWAP edx [486] | 0F CA | | 2 | --------- |
| BSWAP ebx [486] | 0F CB | | 2 | --------- |
| BSWAP esp [486] | 0F CC | | 2 | --------- |
| BSWAP ebp [486] | 0F CD | | 2 | --------- |
| BSWAP esi [486] | 0F CE | | 2 | --------- |
| BSWAP edi [486] | 0F CF | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: BSWAP reg32
Modifies flags: none
Changes the byte order of a 32 bit register from big endian to
little endian or vice versa. Result left in destination register
is undefined if the operand is a 16 bit register.
BT - Bit Test (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BT rmw,ib [386] | 0F BA /4 d0 d1 i0 | | 4~6 | --------c |
| BT rmw,rw [386] | 0F A3 mr d0 d1 | | 3~5 | --------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: BT dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag.
BTC - Bit Test with Compliment (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BTC rmw,ib [386] | 0F BA /7 d0 d1 i0 | | 4~6 | --------c |
| BTC rmw,rw [386] | 0F BB mr d0 d1 | | 3~5 | --------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: BTC dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag after being complimented (inverted).
BTR - Bit Test with Reset (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BTR rmw,ib [386] | 0F BA /6 d0 d1 i0 | | 4~6 | --------c |
| BTR rmw,rw [386] | 0F B3 mr d0 d1 | | 3~5 | --------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: BTR dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag and then cleared in the destination.
BTS - Bit Test and Set (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| BTS rmw,ib [386] | 0F BA /5 d0 d1 i0 | | 4~6 | --------c |
| BTS rmw,rw [386] | 0F AB mr d0 d1 | | 3~5 | --------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: BTS dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag and then set in the destination.
CALL - Procedure Call
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CALL np | E8 o0 o1 | | 3 | --------- |
| CALL rw | FF /2 d0 d1 | W | 2~4 | --------- |
| CALL DWORD PTR[rw] | FF /3 d0 d1 | W | 2~4 | --------- |
| CALL FAR PTR fp | 9A o0 o1 sl sh | | 5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CALL destination
Modifies flags: None
Pushes Instruction Pointer (and Code Segment for far calls) onto
stack and loads Instruction Pointer with the address of proc-name.
Code continues with execution at CS:IP.
CBW - Convert Byte to Word
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CBW | 98 | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CBW
Modifies flags: None
Converts byte in AL to word Value in AX by extending sign of AL
throughout register AH.
CDQ - Convert Double to Quad (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CDQ | ? ? ? ? ? ? | | ? | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CDQ
Modifies flags: None
Converts signed DWORD in EAX to a signed quad word in EDX:EAX by
extending the high order bit of EAX throughout EDX
CLC - Clear Carry
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CLC | F8 | | 1 | --------0 |
+---------------------------+-------------------+----+-----+-----------+
Usage: CLC
Modifies flags: CF
Clears the Carry Flag.
CLD - Clear Direction Flag
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CLD | FC | | 1 | -0------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CLD
Modifies flags: DF
Clears the Direction Flag causing string instructions to increment
the SI and DI index registers.
CLI - Clear Interrupt Flag (disable)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CLI | FA | | 1 | --0------ |
+---------------------------+-------------------+----+-----+-----------+
Usage: CLI
Modifies flags: IF
Disables the maskable hardware interrupts by clearing the Interrupt
flag. NMI's and software interrupts are not inhibited.
CLTS - Clear Task Switched Flag (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CLTS [286] | 0F 06 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CLTS
Modifies flags: None
Clears the Task Switched Flag in the Machine Status Register. This
is a privileged operation and is generally used only by operating
system code.
CMC - Complement Carry Flag
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CMC | F5 | | 1 | --------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: CMC
Modifies flags: CF
Toggles (inverts) the Carry Flag
CMP - Compare
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CMP AL,ib | 3C i0 | B | 2 | o---szapc |
| CMP AX,iw | 3D i0 i1 | W | 3 | o---szapc |
| CMP rb,rmb | 3A mr d0 d1 | B | 2~4 | o---szapc |
| CMP rw,rmw | 3B mr d0 d1 | W | 2~4 | o---szapc |
| CMP rmb,ib | 80 /7 d0 d1 i0 | NB | 3~5 | o---szapc |
| CMP rmw,iw | 81 /7 d0 d1 i0 i1 | NW | 4~6 | o---szapc |
| CMP rmw,ib | 83 /7 d0 d1 i0 | EW | 3~5 | o---szapc |
| CMP rmb,rb | 38 mr d0 d1 | B | 2~4 | o---szapc |
| CMP rmw,rw | 39 mr d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: CMP dest,src
Modifies flags: AF CF OF PF SF ZF
Subtracts source from destination and updates the flags but does
not save result. Flags can subsequently be checked for conditions.
CMPS - Compare String (Byte, Word or Doubleword)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CMPSB | A6 | B | 1 | od--szapc |
| CMPSW | A7 | W | 1 | od--szapc |
| CMPSD | ? | D | 1 | od--szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: CMPS dest,src
CMPSB
CMPSW
CMPSD (386+ only)
Modifies flags: AF CF OF PF SF ZF
Subtracts destination value from source without saving results.
Updates flags based on the subtraction and the index registers
(E)SI and (E)DI are incremented or decremented depending on the
state of the Direction Flag. CMPSB inc/decrements the index
registers by 1, CMPSW inc/decrements by 2, while CMPSD increments
or decrements by 4. The REP prefixes can be used to process
entire data items.
CMPXCHG/CMPXCHG8B - Compare and Exchange
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CMPXCHG rmb,rb [486] | 0F A6 mr d0 d1 | B | 3~5 | o---szapc |
| CMPXCHG rmw,rw [486] | 0F A7 mr d0 d1 | W | 3~5 | o---szapc |
| CMPXCHG rmb,rb [486] | 0F B0 mr d0 d1 | B | 3~5 | o---szapc |
| CMPXCHG rmw,rw [486] | 0F B1 mr d0 d1 | W | 3~5 | o---szapc |
| CMPXCHG8B rmq,rd [P5] | 0F C7 mr d0 d1 | | 3~5 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CMPXCHG dest,src (486+)
CMPXCHG8B dest, src (P5+)
Modifies flags: AF CF OF PF SF ZF
Compares the accumulator (8-32 bits) with "dest". If equal the
"dest" is loaded with "src", otherwise the accumulator is loaded
with "dest".
CWD - Convert Word to Doubleword
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CWD | 99 | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CWD
Modifies flags: None
Extends sign of word in register AX throughout register DX forming
a doubleword quantity in DX:AX.
CWDE - Convert Word to Extended Doubleword (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| CWDE | ? | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: CWDE
Modifies flags: None
Converts a signed word in AX to a signed doubleword in EAX by
extending the sign bit of AX throughout EAX.
DAA - Decimal Adjust for Addition
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| DAA | 27 | | 1 | ----szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: DAA
Modifies flags: AF CF PF SF ZF (OF undefined)
Corrects result (in AL) of a previous BCD addition operation.
Contents of AL are changed to a pair of packed decimal digits.
DAS - Decimal Adjust for Subtraction
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| DAS | 2F | | 1 | ----szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: DAS
Modifies flags: AF CF PF SF ZF (OF undefined)
Corrects result (in AL) of a previous BCD subtraction operation.
Contents of AL are changed to a pair of packed decimal digits.
DEC - Decrement
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| DEC AX | 48 | | 1 | o---szap- |
| DEC BP | 4C | | 1 | o---szap- |
| DEC BX | 4A | | 1 | o---szap- |
| DEC CX | 49 | | 1 | o---szap- |
| DEC DI | 4F | | 1 | o---szap- |
| DEC DX | 49 | | 1 | o---szap- |
| DEC rmb | FE /1 d0 d1 | | 2~4 | o---szap- |
| DEC rmw | FF /1 d0 d1 | | 2~4 | o---szap- |
| DEC SI | 4D | | 1 | o---szap- |
| DEC SP | 4B | | 1 | o---szap- |
+---------------------------+-------------------+----+-----+-----------+
Usage: DEC dest
Modifies flags: AF OF PF SF ZF
Unsigned binary subtraction of one from the destination.
DIV - Divide
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| DIV rmb | F6 /6 d0 d1 | B | 2~4 | o---szapc |
| DIV rmw | F7 /6 d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: DIV src
Modifies flags: (AF,CF,OF,PF,SF,ZF undefined)
Unsigned binary division of accumulator by source. If the source
divisor is a byte value then AX is divided by "src" and the quotient
is placed in AL and the remainder in AH. If source operand is a word
value, then DX:AX is divided by "src" and the quotient is stored in AX
and the remainder in DX.
ENTER - Make Stack Frame (80188+)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| ENTER iw,ib [186] | C8 i0 i1 i0 | | 4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: ENTER locals,level
Modifies flags: None
Modifies stack for entry to procedure for high level language.
Operand "locals" specifies the amount of storage to be allocated
on the stack. "Level" specifies the nesting level of the routine.
Paired with the LEAVE instruction, this is an efficient method of
entry and exit to procedures.
A description of the floating point instructions is not available at yet.
The following table has been provided for op-codes:
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| F2XM1 | D9 F0 | | 2 | --------- |
| FABS | D9 E1 | | 2 | --------- |
| FADD | DE C1 | | 2 | --------- |
| FADD mdr | D8 /0 d0 d1 | D | 2~4 | --------- |
| FADD mqr | DC /0 d0 d1 | Q | 2~4 | --------- |
| FADD st(i),st | DC C0+i | | 2 | --------- |
| FADD st,st(i) | D8 C0+i | | 2 | --------- |
| FADDP st(i),st | DE C0+i | | 2 | --------- |
| FBLD mtr | DF /4 d0 d1 | | 2~4 | --------- |
| FBSTP mtr | DF /6 d0 d1 | | 2~4 | --------- |
| FCHS | D9 E0 | | 2 | --------- |
| FCLEX | 9B DB E2 | | 3 | --------- |
| FCOM | D8 D1 | | 2 | -----z-pc |
| FCOM mdr | D8 /2 d0 d1 | D | 2~4 | -----z-pc |
| FCOM mqr | DC /2 d0 d1 | Q | 2~4 | -----z-pc |
| FCOM st(i) | D8 D0+i | | 2 | -----z-pc |
| FCOMP | D8 D9 | | 2 | -----z-pc |
| FCOMP mdr | D8 /3 d0 d1 | D | 2~4 | -----z-pc |
| FCOMP mqr | DC /3 d0 d1 | Q | 2~4 | -----z-pc |
| FCOMP st(i) | D8 D8+i | | 2 | -----z-pc |
| FCOMPP | DE D9 | | 2 | -----z-pc |
| FCOS [387] | D9 FF | | 2 | --------- |
| FDECSTP | D9 F6 | | 2 | --------- |
| FDISI | 9B DB E1 | | 3 | --------- |
| FDIV mdr | D8 /6 d0 d1 | D | 2~4 | --------- |
| FDIV mqr | DC /6 d0 d1 | Q | 2~4 | --------- |
| FDIV st(i),st | DC F8+i | | 2 | --------- |
| FDIV st,st(i) | DC F0+i | | 2 | --------- |
| FDIVP | DE F9 | | 2 | --------- |
| FDIVP st(i),st | DE F8+i | | 2 | --------- |
| FDIVR mdr | D8 /7 d0 d1 | D | 2~4 | --------- |
| FDIVR mqr | DC /7 d0 d1 | Q | 2~4 | --------- |
| FDIVR st(i),st | DC F0+i | | 2 | --------- |
| FDIVR st,st(i) | DC F8+i | | 2 | --------- |
| FDIVRP | DE F1 | | 2 | --------- |
| FDIVRP st(i),st | DE F0+i | | 2 | --------- |
| FENI | 9B DB E0 | | 3 | --------- |
| FFREE st(i) | DD C0+i | | 2 | --------- |
| FIADD mw | DE /0 d0 d1 | W | 2~4 | --------- |
| FIADD md | DA /0 d0 d1 | D | 2~4 | --------- |
| FICOM mdr | DE /2 d0 d1 | D | 2~4 | -----z-pc |
| FICOM mqr | DA /2 d0 d1 | Q | 2~4 | -----z-pc |
| FICOMP md | DE /3 d0 d1 | D | 2~4 | -----z-pc |
| FICOMP mq | DA /3 d0 d1 | Q | 2~4 | -----z-pc |
| FIDIV mw | DE /6 d0 d1 | W | 2~4 | --------- |
| FIDIV md | DA /6 d0 d1 | D | 2~4 | --------- |
| FIDIVR mw | DE /7 d0 d1 | W | 2~4 | --------- |
| FIDIVR md | DA /7 d0 d1 | D | 2~4 | --------- |
| FILD mw | DF /0 d0 d1 | W | 2~4 | --------- |
| FILD md | DB /0 d0 d1 | D | 2~4 | --------- |
| FILD mq | DF /5 d0 d1 | Q | 2~4 | --------- |
| FIMUL mw | DE /1 d0 d1 | W | 2~4 | --------- |
| FIMUL md | DA /1 d0 d1 | D | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
| FINCSTP | D9 F7 | | 2 | --------- |
| FINIT | 9B DB E3 | | 3 | --------- |
| FIST mw | DF /2 d0 d1 | W | 2~4 | --------- |
| FIST md | DB /2 d0 d1 | D | 2~4 | --------- |
| FISTP mw | DF /3 d0 d1 | W | 2~4 | --------- |
| FISTP md | DB /3 d0 d1 | D | 2~4 | --------- |
| FISTP mq | DF /7 d0 d1 | Q | 2~4 | --------- |
| FISUB mw | DE /4 d0 d1 | W | 2~4 | --------- |
| FISUB md | DA /4 d0 d1 | D | 2~4 | --------- |
| FISUBR mw | DE /5 d0 d1 | W | 2~4 | --------- |
| FISUBR md | DA /5 d0 d1 | D | 2~4 | --------- |
| FLD mdr | D9 /0 d0 d1 | D | 2~4 | --------- |
| FLD mqr | DD /0 d0 d1 | Q | 2~4 | --------- |
| FLD mtr | DB /5 d0 d1 | T | 2~4 | --------- |
| FLD st(i) | D9 C0+i | | 2 | --------- |
| FLD1 | D9 E8 | | 2 | --------- |
| FLDCW mw | D9 /5 d0 d1 | W | 2~4 | --------- |
| FLDENV m14 | D9 /4 d0 d1 | | 2~4 | --------- |
| FLDL2E | D9 EA | | 2 | --------- |
| FLDL2T | D9 E9 | | 2 | --------- |
| FLDLG2 | D9 EC | | 2 | --------- |
| FLDLN2 | D9 ED | | 2 | --------- |
| FLDPI | D9 EB | | 2 | --------- |
| FLDZ | D9 EE | | 2 | --------- |
| FMUL | DE C9 | | 2 | --------- |
| FMUL mdr | D8 /1 d0 d1 | D | 2~4 | --------- |
| FMUL mqr | DC /1 d0 d1 | Q | 2~4 | --------- |
| FMUL st(i),st | DC C8+i | | 2 | --------- |
| FMUL st,st(i) | D8 C8+i | | 2 | --------- |
| FMULP st(i),st | DE C8+i | | 2 | --------- |
| FNCLEX | DB E2 | | 2 | --------- |
| FNDISI | DB E1 | | 2 | --------- |
| FNENI | DB E0 | | 2 | --------- |
| FNINIT | DB E3 | | 2 | --------- |
| FNOP | D9 D0 | | 2 | --------- |
| FNSAVE m94 | DD /6 d0 d1 | | 2~4 | --------- |
| FNSTCW mw | D9 /7 d0 d1 | W | 2~4 | --------- |
| FNSTENV m14 | D9 /6 d0 d1 | | 2~4 | --------- |
| FNSTSW ax | DF E0 | | 2 | --------- |
| FNSTSW mw | DD /7 d0 d1 | W | 2~4 | --------- |
| FPATAN | D9 F3 | | 2 | --------- |
| FPREM | D9 F8 | | 2 | --------- |
| FPREM1 [387] | D9 F5 | | 2 | --------- |
| FPTAN | D9 F2 | | 2 | --------- |
| FRNDINT | D9 FC | | 2 | --------- |
| FRSTOR m94 | DD /4 d0 d1 | | 2~4 | --------- |
| FS: [386] | 64 | | 1 | --------- |
| FSAVE m94 | 9B DD /6 d0 d1 | | 3~5 | --------- |
| FSCALE | D9 FD | | 2 | --------- |
| FSETPM | DB E4 | | 2 | --------- |
| FSIN [387] | D9 FE | | 2 | --------- |
| FSINCOS [387] | D9 FB | | 2 | --------- |
| FSQRT | D9 FA | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
| FST mdr | D9 /2 d0 d1 | D | 2~4 | --------- |
| FST mqr | DD /2 d0 d1 | Q | 2~4 | --------- |
| FST st(i) | DD D0+i | | 2 | --------- |
| FSTCW mw | 9B D9 /7 d0 d1 | W | 3~5 | --------- |
| FSTENV m14 | 9B D9 /6 d0 d1 | | 3~5 | --------- |
| FSTP mdr | D9 /3 d0 d1 | D | 2~4 | --------- |
| FSTP mqr | DD /3 d0 d1 | Q | 2~4 | --------- |
| FSTP mtr | DB /7 d0 d1 | T | 2~4 | --------- |
| FSTP st(i) | DD D8+i | | 2 | --------- |
| FSTSW ax | 9B DF E0 | | 3 | --------- |
| FSTSW mw | 9B DD /7 d0 d1 | W | 3~5 | --------- |
| FSUB mdr | D8 /4 d0 d1 | D | 2~4 | --------- |
| FSUB mqr | DC /4 d0 d1 | Q | 2~4 | --------- |
| FSUB st(i),st | DC E8+i | | 2 | --------- |
| FSUB st,st(i) | D8 E0+i | | 2 | --------- |
| FSUBP | DE E9 | | 2 | --------- |
| FSUBP st(i),st | DE E8+i | | 2 | --------- |
| FSUBR | DE E1 | | 2 | --------- |
| FSUBR mdr | D8 /5 d0 d1 | D | 2~4 | --------- |
| FSUBR mqr | DC /5 d0 d1 | Q | 2~4 | --------- |
| FSUBR st(i),st | DC E0+i | | 2 | --------- |
| FSUBR st,st(i) | D8 E8+i | | 2 | --------- |
| FSUBRP st(i),st | DE E0+i | | 2 | --------- |
| FTST | D9 E4 | | 2 | --------- |
| FUCOM [387] | DD E1 | | 2 | -----z-pc |
| FUCOM st(i) [387] | DD E0+i | | 2 | -----z-pc |
| FUCOMP st(i) [387] | DD E8+i | | 2 | -----z-pc |
| FUCOMPP [387] | DA E9 | | 2 | -----z-pc |
| FXAM | D9 E5 | | 2 | --------- |
| FXCH | D9 C9 | | 2 | --------- |
| FXCH st(i) | D9 C8+i | | 2 | --------- |
| FXTRACT | D9 F4 | | 2 | --------- |
| FYL2X | D9 F1 | | 2 | --------- |
| FYL2XP1 | D9 F9 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
ESC - Escape
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| ESC | ? | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: ESC immed,src
Modifies flags: None
Provides access to the data bus for other resident processors.
The CPU treats it as a NOP but places memory operand on bus.
HLT - Halt CPU
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| HLT | F4 | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: HLT
Modifies flags: None
Halts CPU until RESET line is activated, NMI or maskable interrupt
received. The CPU becomes dormant but retains the current CS:IP
for later restart.
IDIV - Signed Integer Division
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| IDIV rmb | F6 /7 d0 d1 | B | 2~4 | o---szapc |
| IDIV rmw | F7 /7 d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: IDIV src
Modifies flags: (AF,CF,OF,PF,SF,ZF undefined)
Signed binary division of accumulator by source. If source is a
byte value, AX is divided by "src" and the quotient is stored in
AL and the remainder in AH. If source is a word value, DX:AX is
divided by "src", and the quotient is stored in AL and the
remainder in DX.
IMUL - Signed Multiply
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| IMUL rb,rmb [386] | 0F AF mr d0 d1 | B | 3~5 | o---szapc |
| IMUL rd,ib | 6B mr i0 | W | 3 | o---szapc |
| IMUL rd,id | 69 mr i0 i1 i2 i3 | W | 6 | o---szapc |
| IMUL rd,rmd,ib | 6B mr d0 d1 i0 | W | 3~5 | o---szapc |
| IMUL rd,rmd,id | 69 mr d0 d1 i0~i3 | W | 6~8 | o---szapc |
| IMUL rmb | F6 /5 d0 d1 | B | 2~4 | o---szapc |
| IMUL rmw | F7 /5 d0 d1 | W | 2~4 | o---szapc |
| IMUL rw,ib | 6B mr i0 | B | 3 | o---szapc |
| IMUL rw,iw | 69 mr i0 i1 | B | 4 | o---szapc |
| IMUL rw,rmw [386] | 0F AF mr d0 d1 | W | 3~5 | o---szapc |
| IMUL rw,rmw,ib | 6B mr d0 d1 i0 | B | 3~5 | o---szapc |
| IMUL rw,rmw,iw | 69 mr d0 d1 i0 i1 | B | 4~6 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: IMUL src
IMUL src,immed (286+ only)
IMUL dest,src,immed8 (286+ only)
IMUL dest,src (386+ only)
Modifies flags: CF OF (AF,PF,SF,ZF undefined)
Signed multiplication of accumulator by "src" with result placed
in the accumulator. If the source operand is a byte value, it
is multiplied by AL and the result stored in AX. If the source
operand is a word value it is multiplied by AX and the result is
stored in DX:AX. Other variations of this instruction allow
specification of source and destination registers as well as a
third immediate factor.
IN - Input Byte or Word From Port
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| IN AL,ib | E4 i0 | B | 2 | --------- |
| IN AL,DX | EC | B | 1 | --------- |
| IN AX,ib | E5 i0 | W | 2 | --------- |
| IN AX,DX | ED | W | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: IN accum,port
Modifies flags: None
A byte, word or dword is read from "port" and placed in AL, AX or
EAX respectively. If the port number is in the range of 0-255
it can be specified as an immediate, otherwise the port number
must be specified in DX. Valid port ranges on the PC are 0-1024,
though values through 65535 may be specified and recognized by
third party vendors and PS/2's.
INC - Increment
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| INC AX | 40 | | 1 | o---szap- |
| INC CX | 41 | | 1 | o---szap- |
| INC DX | 42 | | 1 | o---szap- |
| INC BX | 43 | | 1 | o---szap- |
| INC SP | 44 | | 1 | o---szap- |
| INC BP | 45 | | 1 | o---szap- |
| INC SI | 46 | | 1 | o---szap- |
| INC DI | 47 | | 1 | o---szap- |
| INC rmb | FE /0 d0 d1 | | 2~4 | o---szap- |
| INC rmw | FF /0 d0 d1 | | 2~4 | o---szap- |
+---------------------------+-------------------+----+-----+-----------+
Usage: INC dest
Modifies flags: AF OF PF SF ZF
Adds one to destination unsigned binary operand.
INS - Input String from Port (80188+)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| INSB [186] | 6C | B | 1 | --------- |
| INSW [186] | 6D | W | 1 | --------- |
| INSD [386] | ? | D | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: INS dest,port
INSB
INSW
INSD (386+ only)
Modifies flags: None
Loads data from port to the destination ES:(E)DI (even if a
destination operand is supplied). (E)DI is adjusted by the size
of the operand and increased if the Direction Flag is cleared and
decreased if the Direction Flag is set. For INSB, INSW, INSD no
operands are allowed and the size is determined by the mnemonic.
INT - Interrupt
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| INT 3 | CC | | 1 | --00----- |
| INT ib | CD i0 | | 2 | --00----- |
+---------------------------+-------------------+----+-----+-----------+
Usage: INT num
Modifies flags: TF IF
Initiates a software interrupt by pushing the flags, clearing the
Trap and Interrupt Flags, pushing CS followed by IP and loading
CS:IP with the value found in the interrupt vector table. Execution
then begins at the location addressed by the new CS:IP
INTO - Interrupt on Overflow
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| INTO | CE | | 1 | --00----- |
+---------------------------+-------------------+----+-----+-----------+
Usage: INTO
Modifies flags: IF TF
If the Overflow Flag is set this instruction generates an INT 4
which causes the code addressed by 0000:0010 to be executed.
INVD - Invalidate Cache (486+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| INVD [486] | 0F 08 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: INVD
Modifies flags: none
Flushes CPU internal cache. Issues special function bus cycle
which indicates to flush external caches. Data in write-back
external caches is lost.
INVLPG - Invalidate Translation Look-Aside Buffer Entry (486+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| INVLPG m [486] | 0F 01 /7 | | 3 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: INVLPG
Modifies flags: none
Invalidates a single page table entry in the Translation
Look-Aside Buffer. Intel warns that this instruction may be
implemented differently on future processors.
IRET/IRETD - Interrupt Return
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| IRET | CF | | 1 | oditszapc |
| IRETD | ? | | 1 | oditszapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: IRET
IRETD (386+ only)
Modifies flags: AF CF DF IF PF SF TF ZF
Returns control to point of interruption by popping IP, CS
and then the Flags from the stack and continues execution at
this location. CPU exception interrupts will return to the
instruction that cause the exception because the CS:IP placed
on the stack during the interrupt is the address of the offending
instruction.
JA/JNBE - Jump Above / Jump Not Below or Equal
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JA ll [386] | 0F 87 r0 r1 | | 4 | --------- |
| JA sl | 77 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JA/JNBE are different mnemonics for the same instruction
Usage: JA label
JNBE label
Modifies flags: None
Causes execution to branch to "label" if the Carry Flag and Zero Flag
are both clear. Unsigned comparision.
JAE/JNB - Jump Above or Equal / Jump on Not Below
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JAE ll [386] | 0F 83 r0 r1 | | 4 | --------- |
| JAE sl | 73 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JAE/JNB are different mnemonics for the same instruction
Usage: JAE label
JNB label
Modifies flags: None
Causes execution to branch to "label" if the Carry Flag is clear.
Functionally similar to JNC. Unsigned comparision.
JB/JNAE - Jump Below / Jump Not Above or Equal
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JB ll [386] | 0F 82 r0 r1 | | 4 | --------- |
| JB sl | 72 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JB/JNAE are different mnemonics for the same instruction
Usage: JB label
JNAE label
Modifies flags: None
Causes execution to branch to "label" if the Carry Flag is set.
Functionally similar to JC. Unsigned comparision.
JBE/JNA - Jump Below or Equal / Jump Not Above
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JBE ll [386] | 0F 86 r0 r1 | | 4 | --------- |
| JBE sl | 76 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JBE/JNA are different mnemonics for the same instruction
Usage: JBE label
JNA label
Modifies flags: None
Causes execution to branch to "label" if the Carry Flag or
the Zero Flag is set. Unsigned comparision.
JC - Jump on Carry
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JC sl | ? r0 | | 2 | --------- |
| JC sl | ? r0 r1 | | 4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JC label
Modifies flags: None
Causes execution to branch to "label" if the Carry Flag is set.
Functionally similar to JB and JNAE. Unsigned comparision.
JCXZ/JECXZ - Jump if Register (E)CX is Zero
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JCXZ sl | E3 r0 | | 2 | --------- |
| JECXZ sl | ? r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JCXZ label
JECXZ label (386+ only)
Modifies flags: None
Causes execution to branch to "label" if register CX is zero. Uses
unsigned comparision.
JE/JZ - Jump Equal / Jump Zero
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JE ll [386] | 0F 84 r0 r1 | | 4 | --------- |
| JE sl | 74 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JE/JZ are different mnemonics for the same instruction
Usage: JE label
JZ label
Modifies flags: None
Causes execution to branch to "label" if the Zero Flag is set. Uses
unsigned comparision.
JG/JNLE - Jump Greater / Jump Not Less or Equal
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JG ll [386] | 0F 8F r0 r1 | | 4 | --------- |
| JG sl | 7F r0 | | 4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JG/JNLE are different mnemonics for the same instruction
Usage: JG label
JNLE label
Modifies flags: None
Causes execution to branch to "label" if the Zero Flag is clear or
the Sign Flag equals the Overflow Flag. Signed comparision.
JGE/JNL - Jump Greater or Equal / Jump Not Less
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JGE ll [386] | ? r0 r1 | | 4 | --------- |
| JGE sl | ? r0 | | 4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JGE/JNL are different mnemonics for the same instruction
Usage: JGE label
JNL label
Modifies flags: None
Causes execution to branch to "label" if the Sign Flag equals
the Overflow Flag. Signed comparision.
JL/JNGE - Jump Less / Jump Not Greater or Equal
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JL ll [386] | 0F 8C r0 r1 | | 4 | --------- |
| JL sl | 7C r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JL/JNGE are different mnemonics for the same instruction
Usage: JL label
JNGE label
Modifies flags: None
Causes execution to branch to "label" if the Sign Flag is not equal
to Overflow Flag. Unsigned comparision.
JLE/JNG - Jump Less or Equal / Jump Not Greater
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JLE ll [386] | ? r0 r1 | | 4 | --------- |
| JLE sl | ? r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JLE/JNG are different mnemonics for the same instruction
Usage: JLE label
JNG label
Modifies flags: None
Causes execution to branch to "label" if the Zero Flag is set or the
Sign Flag is not equal to the Overflow Flag. Signed comparision.
JMP - Unconditional Jump
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JMP SHORT sl | EB r0 | | 2 | --------- |
| JMP np | E9 o0 o1 | | 3 | --------- |
| JMP rmw | FF /4 d0 d1 | | 2~4 | --------- |
| JMP DWORD PTR [rmw] | FF /5 d0 d1 | | 2~4 | --------- |
| JMP FAR PTR fp | EA o0 o1 s0 s1 | | 5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JMP target
Modifies flags: None
Unconditionally transfers control to "label". Jumps by default
are within -32768 to 32767 bytes from the instruction following
the jump. NEAR and SHORT jumps cause the IP to be updated while FAR
jumps cause CS and IP to be updated.
JNC - Jump Not Carry
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JNC s1 (no information) | ? ? ? | | ? | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JNC label
Modifies flags: None
Causes execution to branch to "label" if the Carry Flag is clear.
Functionally similar to JAE or JNB. Unsigned comparision.
JNE/JNZ - Jump Not Equal / Jump Not Zero
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JNE ll [386] | 0F 85 r0 r1 | | 4 | --------- |
| JNE sl | 75 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JNE/JNZ are different mnemonics for the same instruction
Usage: JNE label
JNZ label
Modifies flags: None
Causes execution to branch to "label" if the Zero Flag is clear.
Unsigned comparision.
JNO - Jump Not Overflow
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JNO ll [386] | 0F 81 r0 r1 | | 4 | --------- |
| JNO sl | 71 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JNO label
Modifies flags: None
Causes execution to branch to "label" if the Overflow Flag is clear.
Signed comparision.
JNS - Jump Not Signed
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JNS ll [386] | 0F 89 r0 r1 | | 4 | --------- |
| JNS sl | 79 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JNS label
Modifies flags: None
Causes execution to branch to "label" if the Sign Flag is clear.
Signed comparision.
JNP/JPO - Jump Not Parity / Jump Parity Odd
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JNP ll [386] | 0F 8B r0 r1 | | 4 | --------- |
| JNP sl | 7B r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JNE/JPO are different mnemonics for the same instruction
Usage: JNP label
JPO label
Modifies flags: None
Causes execution to branch to "label" if the Parity Flag is clear.
Unsigned comparision.
JO - Jump on Overflow
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JO ll [386] | 0F 80 r0 r1 | | 4 | --------- |
| JO sl | 70 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JO label
Modifies flags: None
Causes execution to branch to "label" if the Overflow Flag is set.
Signed comparision.
JP/JPE - Jump on Parity / Jump on Parity Even
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JP ll [386] | 0F 8A r0 r1 | | 4 | --------- |
| JP sl | 7A r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* JP/JPE are different mnemonics for the same instruction
Usage: JP label
JPE label
Modifies flags: None
Causes execution to branch to "label" if the Parity Flag is set.
Unsigned comparision.
JS - Jump Signed
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| JS ll [386] | 0F 88 r0 r1 | | 4 | --------- |
| JS sl | 78 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: JS label
Modifies flags: None
Causes execution to branch to "label" if the Sign Flag is set.
Signed comparision.
LAHF - Load Register AH From Flags
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LAHF | 9F | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LAHF
Modifies flags: None
Copies bits 0-7 of the flags register into AH. This includes flags
AF, CF, PF, SF and ZF other bits are undefined.
LAR - Load Access Rights (286+ protected)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LAR rw,rmw [286] | 0F 02 mr d0 d1 | | 3~5 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LAR dest,src
Modifies flags: ZF
The high byte of the of the destination register is overwritten by
the value of the access rights byte and the low order byte is zeroed
depending on the selection in the source operand. The Zero Flag is
set if the load operation is successful.
LDS - Load Pointer Using DS
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LDS rw,md | C5 mr d0 d1 | | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LDS dest,src
Modifies flags: None
Loads 32-bit pointer from memory source to destination register
and DS. The offset is placed in the destination register and the
segment is placed in DS. To use this instruction the word at the
lower memory address must contain the offset and the word at the
higher address must contain the segment. This simplifies the loading
of far pointers from the stack and the interrupt vector table.
LEA - Load Effective Address
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LEA rw,mw | 8D mr d0 d1 | | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LEA dest,src
Modifies flags: None
Transfers offset address of "src" to the destination register.
LEAVE - Restore Stack for Procedure Exit (80188+)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LEAVE [186] | C9 | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LEAVE
Modifies flags: None
Releases the local variables created by the previous ENTER
instruction by restoring SP and BP to their condition before
the procedure stack frame was initialized.
LES - Load Pointer Using ES
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LES rw,md | C4 mr d0 d1 | | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LES dest,src
Modifies flags: None
Loads 32-bit pointer from memory source to destination register
and ES. The offset is placed in the destination register and the
segment is placed in ES. To use this instruction the word at the
lower memory address must contain the offset and the word at the
higher address must contain the segment. This simplifies the loading
of far pointers from the stack and the interrupt vector table.
LFS - Load Pointer Using FS (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LFS rw,md [386] | 0F B4 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LFS dest,src
Modifies flags: None
Loads 32-bit pointer from memory source to destination register
and FS. The offset is placed in the destination register and the
segment is placed in FS. To use this instruction the word at the
lower memory address must contain the offset and the word at the
higher address must contain the segment. This simplifies the loading
of far pointers from the stack and the interrupt vector table.
LGDT - Load Global Descriptor Table (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LGDT mw [286] | 0F 01 /2 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LGDT src
Modifies flags: None
Loads a value from an operand into the Global Descriptor Table
(GDT) register.
LIDT - Load Interrupt Descriptor Table (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LIDT mw [286] | 0F 01 /3 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LIDT src
Modifies flags: None
Loads a value from an operand into the Interrupt Descriptor Table
(IDT) register.
LGS - Load Pointer Using GS (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LGS rw,md [386] | 0F B5 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LGS dest,src
Modifies flags: None
Loads 32-bit pointer from memory source to destination register
and GS. The offset is placed in the destination register and the
segment is placed in GS. To use this instruction the word at the
lower memory address must contain the offset and the word at the
higher address must contain the segment. This simplifies the loading
of far pointers from the stack and the interrupt vector table.
LLDT - Load Local Descriptor Table (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LLDT rmw [286] | 0F 00 /2 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LLDT src
Modifies flags: None
Loads a value from an operand into the Local Descriptor Table
Register (LDTR).
LMSW - Load Machine Status Word (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LMSW rmw [286] | 0F 01 /6 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LMSW src
Modifies flags: None
Loads the Machine Status Word (MSW) from data found at "src"
LOCK - Lock Bus
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LOCK | F0 | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LOCK
LOCK: (386+ prefix)
Modifies flags: None
This instruction is a prefix that causes the CPU assert bus lock
signal during the execution of the next instruction. Used to
avoid two processors from updating the same data location. The
286 always asserts lock during an XCHG with memory operands. This
should only be used to lock the bus prior to XCHG, MOV, IN and
OUT instructions.
LODS - Load String (Byte, Word or Double)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LODSB | AC | B | 1 | --------- |
| LODSW | AD | W | 1 | --------- |
| LODSD | ? | D | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LODS src
LODSB
LODSW
LODSD (386+ only)
Modifies flags: None
Transfers string element addressed by DS:SI (even if an operand is
supplied) to the accumulator. SI is incremented based on the size
of the operand or based on the instruction used. If the Direction
Flag is set SI is decremented, if the Direction Flag is clear SI
is incremented. Use with REP prefixes.
LOOP - Decrement CX and Loop if CX Not Zero
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LOOP sl | E2 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LOOP label
Modifies flags: None
Decrements CX by 1 and transfers control to "label" if CX is not
Zero. The "label" operand must be within -128 or 127 bytes of the
instruction following the loop instruction
LOOPE/LOOPZ - Loop While Equal / Loop While Zero
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LOOPE sl | E1 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* LOOPE/LOOPZ are different mnemonics for the same instruction
Usage: LOOPE label
LOOPZ label
Modifies flags: None
Decrements CX by 1 (without modifying the flags) and transfers
control to "label" if CX != 0 and the Zero Flag is set. The
"label" operand must be within -128 or 127 bytes of the instruction
following the loop instruction.
Clocks Size
Operands 808x 286 386 486 Bytes
label: jump 18 8+m 11+m 9 2
no jump 5 4 ? 6
LOOPNZ/LOOPNE - Loop While Not Zero / Loop While Not Equal
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LOOPNZ sl | E0 r0 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* LOOPNZ/LOOPNE are different mnemonics for the same instruction
Usage: LOOPNZ label
LOOPNE label
Modifies flags: None
Decrements CX by 1 (without modifying the flags) and transfers
control to "label" if CX != 0 and the Zero Flag is clear. The
"label" operand must be within -128 or 127 bytes of the instruction
following the loop instruction.
LSL - Load Segment Limit (286+ protected)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LSL rw,rmw [286] | 0F 03 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LSL dest,src
Modifies flags: ZF
Loads the segment limit of a selector into the destination register
if the selector is valid and visible at the current privilege level.
If loading is successful the Zero Flag is set, otherwise it is
cleared.
LSS - Load Pointer Using SS (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LSS rw,md [386] | 0F B2 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LSS dest,src
Modifies flags: None
Loads 32-bit pointer from memory source to destination register
and SS. The offset is placed in the destination register and the
segment is placed in SS. To use this instruction the word at the
lower memory address must contain the offset and the word at the
higher address must contain the segment. This simplifies the loading
of far pointers from the stack and the interrupt vector table.
LTR - Load Task Register (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| LTR rmw [286] | 0F 00 /3 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: LTR src
Modifies flags: None
Loads the current task register with the value specified in "src".
MOV - Move Byte or Word
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| MOV AL,rmb | A0 d0 d1 | B | 3 | --------- |
| MOV AX,rmw | A1 d0 d1 | W | 3 | --------- |
| MOV AL,ib | B0 i0 | B | 2 | --------- |
| MOV AH,ib | B4 i0 | B | 2 | --------- |
| MOV AX,iw | B8 i0 i1 | W | 3 | --------- |
| MOV CL,ib | B1 i0 | B | 2 | --------- |
| MOV CH,ib | B5 i0 | B | 2 | --------- |
| MOV CX,iw | B9 i0 i1 | W | 3 | --------- |
| MOV DL,ib | B2 i0 | B | 2 | --------- |
| MOV DH,ib | B6 i0 | B | 2 | --------- |
| MOV DX,iw | BA i0 i1 | W | 3 | --------- |
| MOV BL,ib | B3 i0 | B | 2 | --------- |
| MOV BH,ib | B7 i0 | B | 2 | --------- |
| MOV BX,iw | BB i0 i1 | W | 3 | --------- |
| MOV SP,iw | BC i0 i1 | W | 3 | --------- |
| MOV BP,iw | BD i0 i1 | W | 3 | --------- |
| MOV SI,iw | BE i0 i1 | W | 3 | --------- |
| MOV DI,iw | BF i0 i1 | W | 3 | --------- |
| MOV cr,rd [386] | 0F 22 mr | | 3 | --------- |
| MOV rd,cr [386] | 0F 20 mr | | 3 | --------- |
| MOV dr,rd [386] | 0F 23 mr | | 3 | --------- |
| MOV rd,dr [386] | 0F 21 mr | | 3 | --------- |
| MOV tr,rd [386] | 0F 26 mr | | 2 | --------- |
| MOV rd,tr [386] | 0F 24 mr | | 3 | --------- |
| MOV rb,rmb | 8A mr d0 d1 | B | 2~4 | --------- |
| MOV rmb,rb | 88 mr d0 d1 | B | 2~4 | --------- |
| MOV rmb,AL | A2 d0 d1 | B | 3 | --------- |
| MOV rmw,AX | A3 d0 d1 | W | 3 | --------- |
| MOV rmb,ib | C6 mr d0 d1 i0 | B | 3~5 | --------- |
| MOV rmw,iw | C7 mr d0 d1 i0 i1 | W | 4~6 | --------- |
| MOV rmw,rw | 89 mr d0 d1 | W | 2~4 | --------- |
| MOV rw,rmw | 8B mr d0 d1 | W | 2~4 | --------- |
| MOV rmw,sr | 8C mr d0 d1 | | 2~4 | --------- |
| MOV sr,rmw | 8E mr d0 d1 | | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: MOV dest,src
Modifies flags: None
Copies byte or word from the source operand to the destination
operand. If the destination is SS interrupts are disabled except
on early buggy 808x CPUs. Some CPUs disable interrupts if the
destination is any of the segment registers
MOVS - Move String (Byte or Word)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| MOVSB | A4 | B | 1 | --------- |
| MOVSW | A5 | W | 1 | --------- |
| MOVSD | ? | D | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: MOVS dest,src
MOVSB
MOVSW
MOVSD (386+ only)
Modifies flags: None
Copies data from addressed by DS:SI (even if operands are given) to
the location ES:DI destination and updates SI and DI based on the
size of the operand or instruction used. SI and DI are incremented
when the Direction Flag is cleared and decremented when the Direction
Flag is Set. Use with REP prefixes.
MOVSX - Move with Sign Extend (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| MOVSX rw,rmb [386] | 0F BE mr d0 d1 | B | 3~5 | --------- |
| MOVSX rd,rmw [386] | 0F BF mr d0 d1 | W | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: MOVSX dest,src
Modifies flags: None
Copies the value of the source operand to the destination register
with the sign extended.
MOVZX - Move with Zero Extend (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| MOVZX rw,rmb [386] | 0F B6 mr d0 d1 | B | 3~5 | --------- |
| MOVZX rd,rmw [386] | 0F B7 mr d0 d1 | B | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: MOVZX dest,src
Modifies flags: None
Copies the value of the source operand to the destination register
with the zeroes extended.
MUL - Unsigned Multiply
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| MUL rmb | F6 /4 d0 d1 | B | 2~4 | o---szapc |
| MUL rmw | F7 /4 d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: MUL src
Modifies flags: CF OF (AF,PF,SF,ZF undefined)
Unsigned multiply of the accumulator by the source. If "src" is
a byte value, then AL is used as the other multiplicand and the
result is placed in AX. If "src" is a word value, then AX is
multiplied by "src" and DX:AX receives the result. If "src" is
a double word value, then EAX is multiplied by "src" and EDX:EAX
receives the result. The 386+ uses an early out algorithm which
makes multiplying any size value in EAX as fast as in the 8 or 16
bit registers.
NEG - Two's Complement Negation
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| NEG rmb | F6 /3 d0 d1 | B | 2~4 | o---szapc |
| NEG rmw | F7 /3 d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: NEG dest
Modifies flags: AF CF OF PF SF ZF
Subtracts the destination from 0 and saves the 2s complement of
"dest" back into "dest".
NOP - No Operation (90h)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| NOP | 90 | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: NOP
Modifies flags: None
This is a do nothing instruction. It results in occupation of both
space and time and is most useful for patching :-) code [segments].
NOT - One's Compliment Negation (Logical NOT)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| NOT rmb | F6 /2 d0 d1 | B | 2~4 | --------- |
| NOT rmw | F7 /2 d0 d1 | W | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: NOT dest
Modifies flags: None
Inverts the bits of the "dest" operand forming the 1s complement.
OR - Inclusive Logical OR
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| OR AL,ib | 0C i0 | B | 2 | o---szapc |
| OR AX,iw | 0D i0 i1 | W | 3 | o---szapc |
| OR rb,rmb | 0A mr d0 d1 | B | 2~4 | o---szapc |
| OR rw,rmw | 0B mr d0 d1 | W | 2~4 | o---szapc |
| OR rmb,ib | 80 /1 d0 d1 i0 | NB | 3~5 | o---szapc |
| OR rmw,iw | 81 /1 d0 d1 i0 i1 | NW | 4~6 | o---szapc |
| OR rmw,ib | 83 /1 d0 d1 i0 | EW | 3~5 | o---szapc |
| OR rmb,rb | 08 mr d0 d1 | B | 2~4 | o---szapc |
| OR rmw,rw | 09 mr d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: OR dest,src
Modifies flags: CF OF PF SF ZF (AF undefined)
Logical inclusive OR of the two operands returning the result in
the destination. Any bit set in either operand will be set in the
destination.
OUT - Output Data to Port
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| OUT DX,AL | EE | B | 1 | --------- |
| OUT DX,AX | EF | W | 1 | --------- |
| OUT ib,AL | E6 i0 | B | 2 | --------- |
| OUT ib,AX | E7 i0 | W | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: OUT port,accum
Modifies flags: None
Transfers byte in AL,word in AX or dword in EAX to the specified
hardware port address. If the port number is in the range of 0-255
it can be specified as an immediate. If greater than 255 then the
port number must be specified in DX. Since the PC only decodes 10
bits of the port address, values over 1023 can only be decoded by
third party vendor equipment and also map to the port range 0-1023.
OUTS - Output String to Port (80188+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| OUTSB [186] | 6E | B | 1 | --------- |
| OUTSW [186] | 6F | W | 1 | --------- |
| OUTSD [386] | ? | D | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: OUTS port,src
OUTSB
OUTSW
OUTSD (386+ only)
Modifies flags: None
Transfers a byte, word or doubleword from "src" to the hardware
port specified in DX. For instructions with no operands the "src"
is located at DS:SI and SI is incremented or decremented by the
size of the operand or the size dictated by the instruction format.
When the Direction Flag is set SI is decremented, when clear, SI is
incremented. If the port number is in the range of 0-255 it can
be specified as an immediate. If greater than 255 then the port
number must be specified in DX. Since the PC only decodes 10 bits
of the port address, values over 1023 can only be decoded by third
party vendor equipment and also map to the port range 0-1023.
POP - Pop Word off Stack
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| POP AX | 58 | | 1 | --------- |
| POP CX | 59 | | 1 | --------- |
| POP DX | 5A | | 1 | --------- |
| POP BX | 5B | | 1 | --------- |
| POP SP | 5C | | 1 | --------- |
| POP BP | 5D | | 1 | --------- |
| POP SI | 5E | | 1 | --------- |
| POP DI | 5F | | 1 | --------- |
| POP ES | 07 | | 1 | --------- |
| POP SS | 17 | | 1 | --------- |
| POP DS | 1F | | 1 | --------- |
| POP FS [386] | 0F A1 | | 2 | --------- |
| POP GS [386] | 0F A9 | | 2 | --------- |
| POP rmw | 8F mr d0 d1 | | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: POP dest
Modifies flags: None
Transfers word at the current stack top (SS:SP) to the destination
then increments SP by two to point to the new stack top. CS is not
a valid destination.
POPA/POPAD - Pop All Registers onto Stack (80188+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| POPA [186] | 61 | | 1 | --------- |
| POPAD [386] | ? | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: POPA
POPAD (386+ only)
Modifies flags: None
Pops the top 8 words off the stack into the 8 general purpose 16/32
bit registers. Registers are popped in the following order: (E)DI,
(E)SI, (E)BP, (E)SP, (E)DX, (E)CX and (E)AX. The (E)SP value popped
from the stack is actually discarded.
POPF/POPFD - Pop Flags off Stack
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| POPF | 9D | | 1 | oditszapc |
| POPFD | ? | | 1 | oditszapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: POPF
POPFD (386+ only)
Modifies flags: all flags
Pops word/doubleword from stack into the Flags Register and then
increments SP by 2 (for POPF) or 4 (for POPFD).
PUSH - Push Word onto Stack
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| PUSH AX | 50 | | 1 | --------- |
| PUSH CX | 51 | | 1 | --------- |
| PUSH DX | 52 | | 1 | --------- |
| PUSH BX | 53 | | 1 | --------- |
| PUSH SP | 54 | | 1 | --------- |
| PUSH BP | 55 | | 1 | --------- |
| PUSH SI | 56 | | 1 | --------- |
| PUSH DI | 57 | | 1 | --------- |
| PUSH ES | 06 | | 1 | --------- |
| PUSH CS | 0E | | 1 | --------- |
| PUSH SS | 16 | | 1 | --------- |
| PUSH DS | 1E | | 1 | --------- |
| PUSH FS [386] | 0F A0 | | 2 | --------- |
| PUSH GS [386] | 0F A8 | | 2 | --------- |
| PUSH ib [186] | 6A i0 | E | 2 | --------- |
| PUSH iw [186] | 68 i0 i1 | N | 3 | --------- |
| PUSH rmw | FF /6 d0 d1 | | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: PUSH src
PUSH immed (80188+ only)
Modifies flags: None
Decrements SP by the size of the operand (two or four, byte values
are sign extended) and transfers one word from source to the stack
top (SS:SP).
PUSHA/PUSHAD - Push All Registers onto Stack (80188+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| PUSHA [186] | 60 | | 1 | --------- |
| PUSHAD [386] | ? | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: PUSHA
PUSHAD (386+ only)
Modifies flags: None
Pushes all general purpose registers onto the stack in the following
order: (E)AX, (E)CX, (E)DX, (E)BX, (E)SP, (E)BP, (E)SI, (E)DI. The
value of SP is the value before the actual push of SP.
PUSHF/PUSHFD - Push Flags onto Stack
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| PUSHF | 9C | | 1 | --------- |
| PUSHFD | ? | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: PUSHF
PUSHFD (386+ only)
Modifies flags: None
Transfers the Flags Register onto the stack. PUSHF saves a 16 bit
value while PUSHFD saves a 32 bit value.
RCL - Rotate Through Carry Left
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| RCL rmb,1 | D0 /2 d0 d1 | B | 2~4 | o-------c |
| RCL rmb,CL | D2 /2 d0 d1 | B | 2~4 | o-------c |
| RCL rmb,ib [186] | C0 /2 d0 d1 i0 | B | 3~5 | o-------c |
| RCL rmw,1 | D1 /2 d0 d1 | W | 2~4 | o-------c |
| RCL rmw,CL | D3 /2 d0 d1 | W | 2~4 | o-------c |
| RCL rmw,ib [186] | C1 /2 d0 d1 i0 | W | 3~5 | o-------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: RCL dest,count
Modifies flags: CF OF
Rotates the bits in the destination to the left "count" times with
all data pushed out the left side re-entering on the right. The
Carry Flag holds the last bit rotated out.
RCR - Rotate Through Carry Right
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| RCR rmb,1 | D0 /3 d0 d1 | B | 2~4 | o-------c |
| RCR rmb,CL | D2 /3 d0 d1 | B | 2~4 | o-------c |
| RCR rmb,ib [186] | C0 /3 d0 d1 i0 | B | 3~5 | o-------c |
| RCR rmw,1 | D1 /3 d0 d1 | W | 2~4 | o-------c |
| RCR rmw,CL | D3 /3 d0 d1 | W | 2~4 | o-------c |
| RCR rmw,ib [186] | C1 /3 d0 d1 i0 | W | 3~5 | o-------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: RCR dest,count
Modifies flags: CF OF
Rotates the bits in the destination to the right "count" times with
all data pushed out the right side re-entering on the left. The
Carry Flag holds the last bit rotated out.
REP - Repeat String Operation
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| REP | F3 | | 1 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: REP
Modifies flags: None
Repeats execution of string instructions while CX != 0. After
each string operation, CX is decremented and the Zero Flag is
tested. The combination of a repeat prefix and a segment override
on CPU's before the 386 may result in errors if an interrupt occurs
before CX=0. The following code shows code that is susceptible to
this and how to avoid it:
again: rep movs byte ptr ES:[DI],ES:[SI] ; vulnerable instr.
jcxz next ; continue if REP successful
loop again ; interrupt goofed count
next:
REPE/REPZ - Repeat Equal / Repeat Zero
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| REPE | ? | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* REPE/REPZ are different mnemonics for the same instruction
Usage: REPE
REPZ
Modifies flags: None
Repeats execution of string instructions while CX != 0 and the Zero
Flag is set. CX is decremented and the Zero Flag tested after
each string operation. The combination of a repeat prefix and a
segment override on processors other than the 386 may result in
errors if an interrupt occurs before CX=0.
REPNE/REPNZ - Repeat Not Equal / Repeat Not Zero
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| REPNE | F2 | | 1 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
* REPNE/REPNZ are different mnemonics for the same instruction
Usage: REPNE
REPNZ
Modifies flags: None
Repeats execution of string instructions while CX != 0 and the Zero
Flag is clear. CX is decremented and the Zero Flag tested after
each string operation. The combination of a repeat prefix and a
segment override on processors other than the 386 may result in
errors if an interrupt occurs before CX=0.
RET/RETF - Return From Procedure
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| RET | C3 | | 1 | --------- |
| RET iw | C2 i0 i1 | | 3 | --------- |
| RETF | CB | | 1 | --------- |
| RETF iw | CA i0 i1 | | 3 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: RET nBytes
RETF nBytes
RETN nBytes
Modifies flags: None
Transfers control from a procedure back to the instruction address
saved on the stack. "n bytes" is an optional number of bytes to
release. Far returns pop the IP followed by the CS, while near
returns pop only the IP register.
ROL - Rotate Left
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| ROL rmb,1 | D0 /0 d0 d1 | B | 2~4 | o-------c |
| ROL rmb,CL | D2 /0 d0 d1 | B | 2~4 | o-------c |
| ROL rmb,ib [186] | C0 /0 d0 d1 i0 | B | 3~5 | o-------c |
| ROL rmw,1 | D1 /0 d0 d1 | W | 2~4 | o-------c |
| ROL rmw,CL | D3 /0 d0 d1 | W | 2~4 | o-------c |
| ROL rmw,ib [186] | C1 /0 d0 d1 i0 | W | 3~5 | o-------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: ROL dest,count
Modifies flags: CF OF
Rotates the bits in the destination to the left "count" times with
all data pushed out the left side re-entering on the right. The
Carry Flag will contain the value of the last bit rotated out.
ROR - Rotate Right
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| ROR rmb,1 | D0 /1 d0 d1 | B | 2~4 | o-------c |
| ROR rmb,CL | D2 /1 d0 d1 | B | 2~4 | o-------c |
| ROR rmb,ib [186] | C0 /1 d0 d1 i0 | B | 3~5 | o-------c |
| ROR rmw,1 | D1 /1 d0 d1 | W | 2~4 | o-------c |
| ROR rmw,CL | D3 /1 d0 d1 | W | 2~4 | o-------c |
| ROR rmw,ib [186] | C1 /1 d0 d1 i0 | W | 3~5 | o-------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: ROR dest,count
Modifies flags: CF OF
Rotates the bits in the destination to the right "count" times with
all data pushed out the right side re-entering on the left. The
Carry Flag will contain the value of the last bit rotated out.
SAHF - Store AH Register into FLAGS
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SAHF | 9E | | 1 | ----szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: SAHF
Modifies flags: AF CF PF SF ZF
Transfers bits 0-7 of AH into the Flags Register. This includes
AF, CF, PF, SF and ZF.
SAL/SHL - Shift Arithmetic Left / Shift Logical Left
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SAL rmb,1 | D0 /4 d0 d1 | B | 2~4 | o-------c |
| SAL rmb,CL | D2 /4 d0 d1 | B | 2~4 | o-------c |
| SAL rmb,ib [186] | C0 /4 d0 d1 i0 | B | 3~5 | o-------c |
| SAL rmw,1 | D1 /4 d0 d1 | W | 2~4 | o-------c |
| SAL rmw,CL | D3 /4 d0 d1 | W | 2~4 | o-------c |
| SAL rmw,ib [186] | C1 /4 d0 d1 i0 | W | 3~5 | o-------c |
| SHL rmb,1 | D0 /4 d0 d1 | B | 2~4 | o-------c |
| SHL rmb,CL | D2 /4 d0 d1 | B | 2~4 | o-------c |
| SHL rmb,ib [186] | C0 /4 d0 d1 i0 | B | 3~5 | o-------c |
| SHL rmw,1 | D1 /4 d0 d1 | W | 2~4 | o-------c |
| SHL rmw,CL | D3 /4 d0 d1 | W | 2~4 | o-------c |
| SHL rmw,ib [186] | C1 /4 d0 d1 i0 | W | 3~5 | o-------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: SAL dest,count
SHL dest,count
Modifies flags: CF OF PF SF ZF (AF undefined)
Shifts the destination left by "count" bits with zeroes shifted
in on right. The Carry Flag contains the last bit shifted out.
SAR - Shift Arithmetic Right
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SAR rmb,CL | D2 /7 d0 d1 | B | 2~4 | o-------c |
| SAR rmb,ib [186] | C0 /7 d0 d1 i0 | B | 3~5 | o-------c |
| SAR rmw,1 | D1 /7 d0 d1 | W | 2~4 | o-------c |
| SAR rmw,CL | D3 /7 d0 d1 | W | 2~4 | o-------c |
| SAR rmw,ib [186] | C1 /7 d0 d1 i0 | W | 3~5 | o-------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: SAR dest,count
Modifies flags: CF OF PF SF ZF (AF undefined)
Shifts the destination right by "count" bits with the current sign
bit replicated in the leftmost bit. The Carry Flag contains the
last bit shifted out.
SBB - Subtract with Borrow
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SBB AL,ib | 1C i0 | B | 2 | o---szapc |
| SBB AX,iw | 1D i0 i1 | W | 3 | o---szapc |
| SBB rb,rmb | 1A mr d0 d1 | B | 2~4 | o---szapc |
| SBB rw,rmw | 1B mr d0 d1 | W | 2~4 | o---szapc |
| SBB rmb,ib | 80 /3 d0 d1 i0 | NB | 3~5 | o---szapc |
| SBB rmw,iw | 81 /3 d0 d1 i0 i1 | NW | 4~6 | o---szapc |
| SBB rmw,ib | 83 /3 d0 d1 i0 | EW | 3~5 | o---szapc |
| SBB rmb,rb | 18 mr d0 d1 | B | 2~4 | o---szapc |
| SBB rmw,rw | 19 mr d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: SBB dest,src
Modifies flags: AF CF OF PF SF ZF
Subtracts the source from the destination, and subtracts 1 extra if
the Carry Flag is set. Results are returned in "dest".
SCAS - Scan String (Byte, Word or Doubleword)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SCASB | AE | B | 1 | o---szapc |
| SCASW | AF | W | 1 | o---szapc |
| SCASD [386] | ? | D | 1 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: SCAS string
SCASB
SCASW
SCASD (386+ only)
Modifies flags: AF CF OF PF SF ZF
Compares value at ES:DI (even if operand is specified) from the
accumulator and sets the flags similar to a subtraction. DI is
incremented/decremented based on the instruction format (or
operand size) and the state of the Direction Flag. Use with REP
prefixes.
SETAE/SETNB - Set if Above or Equal / Set if Not Below
(unsigned, 386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETAE rmb [386] | 0F 93 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETAE/SETNB are different mnemonics for the same instruction
Usage: SETAE dest
SETNB dest
Modifies flags: none
Sets the byte in the operand to 1 if the Carry Flag is clear
otherwise sets the operand to 0.
SETB/SETNAE - Set if Below / Set if Not Above or Equal
(unsigned, 386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETB rmb [386] | 0F 92 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETB/SETAE are different mnemonics for the same instruction
Usage: SETB dest
SETNAE dest
Modifies flags: none
Sets the byte in the operand to 1 if the Carry Flag is set
otherwise sets the operand to 0.
SETBE/SETNA - Set if Below or Equal / Set if Not Above
(unsigned, 386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETBE rmb [386] | 0F 96 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETBE/SETNA are different mnemonics for the same instruction
Usage: SETBE dest
SETNA dest
Modifies flags: none
Sets the byte in the operand to 1 if the Carry Flag or the Zero
Flag is set, otherwise sets the operand to 0.
SETE/SETZ - Set if Equal / Set if Zero (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETZ rmb [386] | 0F 94 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETE/SETZ are different mnemonics for the same instruction
Usage: SETE dest
SETZ dest
Modifies flags: none
Sets the byte in the operand to 1 if the Zero Flag is set,
otherwise sets the operand to 0.
SETNE/SETNZ - Set if Not Equal / Set if Not Zero (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETNE rmb [386] | 0F 95 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETNE/SETNZ are different mnemonics for the same instruction
Usage: SETNE dest
SETNZ dest
Modifies flags: none
Sets the byte in the operand to 1 if the Zero Flag is clear,
otherwise sets the operand to 0.
SETL/SETNGE - Set if Less / Set if Not Greater or Equal
(signed, 386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETL rmb [386] | 0F 9C mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETL/SETNGE are different mnemonics for the same instruction
Usage: SETL dest
SETNGE dest
Modifies flags: none
Sets the byte in the operand to 1 if the Sign Flag is not equal
to the Overflow Flag, otherwise sets the operand to 0.
SETGE/SETNL - Set if Greater or Equal / Set if Not Less
(signed, 386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETGE rmb [386] | 0F 9D mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETGE/SETNL are different mnemonics for the same instruction
Usage: SETGE dest
SETNL dest
Modifies flags: none
Sets the byte in the operand to 1 if the Sign Flag equals the
Overflow Flag, otherwise sets the operand to 0.
SETLE/SETNG - Set if Less or Equal / Set if Not greater or Equal
(signed, 386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETLE rmb [386] | 0F 9E mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETLE/SETNG are different mnemonics for the same instruction
Usage: SETLE dest
SETNG dest
Modifies flags: none
Sets the byte in the operand to 1 if the Zero Flag is set or the
Sign Flag is not equal to the Overflow Flag, otherwise sets the
operand to 0.
SETG/SETNLE - Set if Greater / Set if Not Less or Equal
(signed, 386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETG rmb [386] | 0F 9F mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETG/SETNLE are different mnemonics for the same instruction
Usage: SETG dest
SETNLE dest
Modifies flags: none
Sets the byte in the operand to 1 if the Zero Flag is clear or the
Sign Flag equals to the Overflow Flag, otherwise sets the operand
to 0.
SETS - Set if Signed (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETS rmb [386] | 0F 98 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SETS dest
Modifies flags: none
Sets the byte in the operand to 1 if the Sign Flag is set, otherwise
sets the operand to 0.
SETNS - Set if Not Signed (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETNS rmb [386] | 0F 99 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SETNS dest
Modifies flags: none
Sets the byte in the operand to 1 if the Sign Flag is clear,
otherwise sets the operand to 0.
SETC - Set if Carry (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETC rmb [386] | ? ? ? ? | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SETC dest
Modifies flags: none
Sets the byte in the operand to 1 if the Carry Flag is set,
otherwise sets the operand to 0.
SETNC - Set if Not Carry (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETNC rmb [386] | ? ? ? ? | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SETNC dest
Modifies flags: none
Sets the byte in the operand to 1 if the Carry Flag is clear,
otherwise sets the operand to 0.
SETO - Set if Overflow (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETO rmb [386] | 0F 90 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SETO dest
Modifies flags: none
Sets the byte in the operand to 1 if the Overflow Flag is set,
otherwise sets the operand to 0.
SETNO - Set if Not Overflow (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETNO rmb [386] | 0F 91 mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SETNO dest
Modifies flags: none
Sets the byte in the operand to 1 if the Overflow Flag is clear,
otherwise sets the operand to 0.
SETP/SETPE - Set if Parity / Set if Parity Even (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETP rmb [386] | 0F 9A mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETP/SETE are different mnemonics for the same instruction
Usage: SETP dest
SETPE dest
Modifies flags: none
Sets the byte in the operand to 1 if the Parity Flag is set,
otherwise sets the operand to 0.
SETNP/SETPO - Set if No Parity / Set if Parity Odd (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SETNP rmb [386] | 0F 9B mr d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
* SETNP/SETPO are different mnemonics for the same instruction
Usage: SETNP dest
SETPO dest
Modifies flags: none
Sets the byte in the operand to 1 if the Parity Flag is clear,
otherwise sets the operand to 0.
SGDT - Store Global Descriptor Table (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SGDT m6 [286] | 0F 01 /0 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SGDT dest
Modifies flags: none
Stores the Global Descriptor Table (GDT) Register into the
specified operand.
SIDT - Store Interrupt Descriptor Table (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SIDT m6 [286] | 0F 01 /1 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SIDT dest
Modifies flags: none
Stores the Interrupt Descriptor Table (IDT) Register into the
specified operand.
SHR - Shift Logical Right
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SHR rmb,1 | D0 /5 d0 d1 | B | 2~4 | o-------c |
| SHR rmb,CL | D2 /5 d0 d1 | B | 2~4 | o-------c |
| SHR rmb,ib [186] | C0 /5 d0 d1 i0 | B | 3~5 | o-------c |
| SHR rmw,1 | D1 /5 d0 d1 | W | 2~4 | o-------c |
| SHR rmw,CL | D3 /5 d0 d1 | W | 2~4 | o-------c |
| SHR rmw,ib [186] | C1 /5 d0 d1 i0 | W | 3~5 | o-------c |
+---------------------------+-------------------+----+-----+-----------+
Usage: SHR dest,count
Modifies flags: CF OF PF SF ZF (AF undefined)
Shifts the destination right by "count" bits with zeroes shifted
in on the left. The Carry Flag contains the last bit shifted out.
SHLD/SHRD - Double Precision Shift (386+ only)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SHLD rmw,rw,CL [386] | 0F A5 mr d0 d1 | | 3~5 | o---szapc |
| SHLD rmw,rw,ib [386] | 0F A4 mr d0 d1 i0 | | 4~6 | o---szapc |
| SHRD rmw,rw,CL [386] | 0F AD mr d0 d1 | | 3~5 | o---szapc |
| SHRD rmw,rw,ib [386] | 0F AC mr d0 d1 i0 | | 4~6 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: SHLD dest,src,count
SHRD dest,src,count
Modifies flags: CF PF SF ZF (OF,AF undefined)
SHLD shifts "dest" to the left "count" times and the bit positions
opened are filled with the most significant bits of "src". SHRD
shifts "dest" to the right "count" times and the bit positions
opened are filled with the least significant bits of the second
operand. Only the 5 lower bits of "count" are used.
SLDT - Store Local Descriptor Table (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SLDT mw [286] | 0F 00 /0 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SLDT dest
Modifies flags: none
Stores the Local Descriptor Table (LDT) Register into the
specified operand.
SMSW - Store Machine Status Word (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SMSW rmw [286] | 0F 01 /4 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: SMSW dest
Modifies flags: none
Store Machine Status Word (MSW) into "dest".
STC - Set Carry
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| STC | F9 | | 1 | --------1 |
+---------------------------+-------------------+----+-----+-----------+
Usage: STC
Modifies flags: CF
Sets the Carry Flag to 1.
STD - Set Direction Flag
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| STD | FD | | 1 | -1------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: STD
Modifies flags: DF
Sets the Direction Flag to 1 causing string instructions to
auto-decrement SI and DI instead of auto-increment.
STI - Set Interrupt Flag (Enable Interrupts)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| STI | FB | | 1 | --1------ |
+---------------------------+-------------------+----+-----+-----------+
Usage: STI
Modifies flags: IF
Sets the Interrupt Flag to 1, enabling recognition of all CPU
hardware interrupts.
STOS - Store String (Byte, Word or Doubleword)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| STOSB | AA | B | 1 | --------- |
| STOSW | AB | W | 1 | --------- |
| STOSD | ? | D | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: STOS dest
STOSB
STOSW
STOSD
Modifies flags: None
Stores value in accumulator to location at ES:(E)DI (even if operand
is given). (E)DI is incremented/decremented based on the size of
the operand (or instruction format) and the state of the Direction
Flag. Use with REP prefixes.
STR - Store Task Register (286+ privileged)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| STR rmw [286] | 0F 01 /1 d0 d1 | | 3~5 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: STR dest
Modifies flags: None
Stores the current Task Register to the specified operand.
SUB - Subtract
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| SUB AL,ib | 2C i0 | B | 2 | o---szapc |
| SUB AX,iw | 2D i0 i1 | W | 3 | o---szapc |
| SUB rb,rmb | 2A mr d0 d1 | B | 2~4 | o---szapc |
| SUB rw,rmw | 2B mr d0 d1 | W | 2~4 | o---szapc |
| SUB rmb,ib | 80 /5 d0 d1 i0 | NB | 3~5 | o---szapc |
| SUB rmw,iw | 81 /5 d0 d1 i0 i1 | NW | 4~6 | o---szapc |
| SUB rmw,ib | 83 /5 d0 d1 i0 | EW | 3~5 | o---szapc |
| SUB rmb,rb | 28 mr d0 d1 | B | 2~4 | o---szapc |
| SUB rmw,rw | 29 mr d0 d1 | W | 2~4 | o---szapc |
+---------------------------+-------------------+----+-----+-----------+
Usage: SUB dest,src
Modifies flags: AF CF OF PF SF ZF
The source is subtracted from the destination and the result is
stored in the destination.
TEST - Test For Bit Pattern
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| TEST AL,ib | A8 i0 | B | 2 | 0---szap0 |
| TEST AX,iw | A9 i0 i1 | W | 3 | 0---szap0 |
| TEST rmb,ib | F6 /0 d0 d1 i0 | B | 3~5 | 0---szap0 |
| TEST rmw,iw | F7 /0 d0 d1 i0 i1 | W | 4~6 | 0---szap0 |
| TEST rmb,rmb | 84 mr d0 d1 | B | 2~4 | 0---szap0 |
| TEST rmw,rmw | 85 mr d0 d1 | W | 2~4 | 0---szap0 |
+---------------------------+-------------------+----+-----+-----------+
Usage: TEST dest,src
Modifies flags: CF OF PF SF ZF (AF undefined)
Performs a logical AND of the two operands updating the flags
register without saving the result.
VERR - Verify Read (286+ protected)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| VERR rmw [286] | 0F 00 /4 d0 d1 | | 3~5 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: VERR src
Modifies flags: ZF
Verifies the specified segment selector is valid and is readable
at the current privilege level. If the segment is readable,
the Zero Flag is set, otherwise it is cleared.
VERW - Verify Write (286+ protected)
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| VERW rmw [286] | 0F 00 /5 d0 d1 | | 3~5 | -----z--- |
+---------------------------+-------------------+----+-----+-----------+
Usage: VERW src
Modifies flags: ZF
Verifies the specified segment selector is valid and is ratable
at the current privilege level. If the segment is writable,
the Zero Flag is set, otherwise it is cleared.
WAIT/FWAIT - Event Wait
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| WAIT | 9B | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: WAIT
FWAIT
Modifies flags: None
CPU enters wait state until the coprocessor signals it has finished
it's operation. This instruction is used to prevent the CPU from
accessing memory that may be temporarily in use by the coprocessor.
WAIT and FWAIT are identical.
WBINVD - Write-Back and Invalidate Cache
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| WBINVD [486] | 0F 09 | | 2 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: WBINVD
Modifies flags: None
Flushes internal cache, then signals the external cache to write
back current data followed by a signal to flush the external cache.
XCHG - Exchange
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| XCHG AX,CX | 91 | | 1 | --------- |
| XCHG AX,DX | 92 | | 1 | --------- |
| XCHG AX,BX | 93 | | 1 | --------- |
| XCHG AX,SP | 94 | | 1 | --------- |
| XCHG AX,BP | 95 | | 1 | --------- |
| XCHG AX,SI | 96 | | 1 | --------- |
| XCHG AX,DI | 97 | | 1 | --------- |
| XCHG rb,rmb | 86 mr d0 d1 | B | 2~4 | --------- |
| XCHG rmb,rb | 86 mr d0 d1 | B | 2~4 | --------- |
| XCHG rmw,rw | 87 mr d0 d1 | W | 2~4 | --------- |
| XCHG rw,rmw | 87 mr d0 d1 | W | 2~4 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: XCHG dest,src
Modifies flags: None
Exchanges contents of source and destination.
XLAT/XLATB - Translate
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| XLAT | D7 | | 1 | --------- |
+---------------------------+-------------------+----+-----+-----------+
Usage: XLAT translation-table
XLATB (masm 5.x)
Modifies flags: None
Replaces the byte in AL with byte from a user table addressed by
BX. The original value of AL is the index into the translate table.
XOR - Exclusive OR
| MNEMONICS | OP XX XX XX XX XX | sw | len | flags |
+---------------------------+-------------------+----+-----+-----------+
| XOR AL,ib | 34 i0 | B | 2 | 0---szap0 |
| XOR AX,iw | 35 i0 i1 | W | 3 | 0---szap0 |
| XOR rb,rmb | 32 mr d0 d1 | B | 2~4 | 0---szap0 |
| XOR rw,rmw | 33 mr d0 d1 | W | 2~4 | 0---szap0 |
| XOR rmb,ib | 80 /6 d0 d1 i0 | NB | 3~5 | 0---szap0 |
| XOR rmw,iw | 81 /6 d0 d1 i0 i1 | NW | 4~6 | 0---szap0 |
| XOR rmw,ib | 83 /6 d0 d1 i0 | EW | 3~5 | 0---szap0 |
| XOR rmb,rb | 30 mr d0 d1 | B | 2~4 | 0---szap0 |
| XOR rmw,rw | 31 mr d0 d1 | W | 2~4 | 0---szap0 |
+---------------------------+-------------------+----+-----+-----------+
Usage: XOR dest,src
Modifies flags: CF OF PF SF ZF (AF undefined)
Performs a bitwise exclusive OR of the operands and returns
the result in the destination.