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CHAPTER 10 Programming Technical Reference - IBM Copyright 1988, Dave Williams LOTUS-INTEL-MICROSOFT EXPANDED MEMORY SPECIFICATION The Expanded Memory Manager ............................................ 10- History ........................................................ 10- Page Frames .................................................... 10- Expanded Memory Services ............................................... 10- AST/Quadram/Ashton-Tate Enhanced EMM ................................... 10- Calling the Manager ............................................ 10- Common EMS Functions (hex calls) 1 (40h) Get Manager Status ............................ 10- 2 (41h) Get Page Frame Segment ........................ 10- 3 (42h) Get Number of Pages ........................... 10- 4 (43h) Get Handle and Allocate Memory ................ 10- 5 (44h) Map Memory .................................... 10- 6 (45h) Release Handle and Memory ..................... 10- 7 (46h) Get EMM Version ............................... 10- 8 (47h) Save Mapping Context .......................... 10- 9 (48h) Restore Mapping Context ....................... 10- 10 (49h) Reserved ...................................... 10- 11 (4Ah) Reserved ...................................... 10- 12 (4Bh) Get Number of EMM Handles ..................... 10- 12 (4Ch) Get Pages Owned By Handle ..................... 10- 14 (4Dh) Get Pages for All Handles ..................... 10- 15 (4Eh) Get Or Set Page Map ........................... 10- new LIM 4.0 specification: 16 (4Fh) Get/Set Partial Page Map ...................... 10- 17 (50h) Map/Unmap Multiple Pages ...................... 10- 18 (51h) Reallocate Pages .............................. 10- 19 (52h) Handle Attribute Functions .................... 10- 20 (53h) Get Handle Name ............................... 10- 21 (54h) Get Handle Directory .......................... 10- 22 (55h) Alter Page Map & Jump ......................... 10- 23 (56h) Alter Page Map & Call ......................... 10- 24 (57h) Move Memory Region ............................ 10- 25 (58h) Get Mappable Physical Address Array ........... 10- 26 (59h) Get Expanded Memory Hardware .................. 10- 27 (5Ah) Allocate Raw Pages ............................ 10- 28 (5Bh) Get Alternate Map Register Set ................ 10- 29 (5Ch) Prepare Expanded Memory Hardware .............. 10- 30 (5Dh) Enable OS/E Function Set ...................... 10- 31 (5Eh) Unknown ....................................... 10- 32 (5Fh) Unknown ....................................... 10- 33 (60h) Unknown ....................................... 10- 34 (61h) AST Generic Accelerator Card Support .......... 10- Expanded Memory Manager Error Codes .................................... 10- THE EXPANDED MEMORY MANAGER History The Lotus/Intel/Microsoft Expanded Memory Manager was originally a Lotus and Intel project and was announced as version 3.0 in the second quarter of 1985 primarily as a means of running larger Lotus worksheets by transparently paging unused sections to bank-switched memory. Shortly afterward Microsoft announced support of the standard and version 3.2 was subsequently released with support for Microsoft Windows. LIM 3.2 supported up to 8 megabytes of paged memory. The LIM 4.0 supports up to 32 megabytes of paged memory. AST/QUADRAM/ASHTON-TATE ENHANCED EXPANDED MEMORY SPECIFICATION The AQA EEMS maintains upward compatibility with the LIM, but is a superset of functions. The AQA EEMS permits its pages to be scattered throughout the unused portion of the machine's address space. On August 19, 1987, the new version of the Expanded Memory Specification (EMS) was announced by Lotus, Intel and Microsoft. This new version of the specification includes many features of the Enhanced Expanded Memory Specification (EEMS) originally developed by AST Reserach, Quadram and Ashton- Tate, although the three original sponsoring companies elected not to make the new specification upward compatible with EEMS. AST Research says that they will endorse EMS 4.0 without reservation. The definitive document for the LIM-EMS is Intel part number 300275-004, August, 1987. 32M ┌──────────────┐ /│ │ │ │ / │ │ │ │ / │ │ │ │ / │ │ │ Expanded │ / │ Memory │ 1024K ┌──────────────┐ │ │ │ / / / / / / │ / │ │ 960K ├──────────────┤ │ │ │ Page Frame │ │ │ │ │ │ │ │ 12 16K-Byte │ │ │ │ Physical │ │ │ │ Pages │ │ │ 768K ├──────────────┤ │ Divided into │ │ / / / / / / │ \ │ logical │ 640K ├──────────────┤ │ pages │ │ │ \ │ │ │ │ │ │ │ │ \ │ │ │ │ │ │ │ 24 16K-Byte │ \ │ │ │ Physical │ │ │ │ Pages* │ \ │ │ │ │ │ │ │ │ \ │ │ │ │ │ │ │ │ \ │ │ 256K ├──────────────┤ │ │ │ │ \ │ │ │ / / / / / / │ │ │ │ │ \ │ │ │ / / / / / / │ │ │ │ │ \ │ │ │ / / / / / / │ │ │ │ │ \ │ │ 0 └──────────────┘ │ │ \ │ │ │ │ \ │ │ 0 └──────────────┘ The page frame is located above the 640k system RAM area, anywhere from 0A000h to 0FFFFh. This area is used by the video adapters, network cards, and add-on ROMs (as in hard disk controllers). The page frames are mapped around areas that are in use. WRITING PROGRAMS THAT USE EXPANDED MEMORY In order to use expanded memory, applications must perform these steps in the following order: 1. Determine if EMM is installed. 2. Determine if enough expanded memory pages exist for your application. (Function 3) 3. Allocate expanded memory pages. (Function 4 or 18) 4. Get the page frame base address. (Function 2) 5. Map in expanded memory pages. (Function 5 or 17) 6. Read/write/execute data in expanded memory, just as if it were conventional memory. 7. Return expanded memory pages to expanded memory pool before exiting. Function 6 or 18) Programming Guidelines The following section contains guidelines for programmers writing applications that use EMM. A) Do not put a program's stack in expanded memory. B) Do not replace interrupt 67h. This is the interrupt vector the EMM uses. Replacing interrupt 67h could result in disabling the Expanded Memory Manager. C) Do not map into conventional memory address space your application doesn't own. Applications that use the EMM to swap into conventional memory space, must first allocate this space from the operating system. If the operating system is not aware that a region of memory it manages is in use, it will think it is available. This could have disastrous results. EMM should not be used to "allocate" conventional memory. DOS is the proper manager of conventional memory space. EMM should only be used to swap data in conventional memory space previously allocated from DOS. D) Applications that plan on using data aliasing in expanded memory must check for the presence of expanded memory hardware. Data aliasing occurs when mapping one logical page into two or more mappable segments. This makes one 16K-byte expanded memory page appear to be in more than one 16K-byte memory address space. Data aliasing is legal and sometimes useful for applications. Software-only expanded memory emulators cannot perform data aliasing. A simple way to distinguish software emulators from actual expanded memory hardware is to attempt data aliasing and check the results. For example, map one logical page into four physical pages. Write to physical page 0. Read physical pages 1-3 to see if the data is there as well. If the data appears in all four physical pages, then expanded memory hardware is installed in the system, and data aliasing is supported. E) Applications should always return expanded memory pages to the expanded memory manager upon termination. These pages will be made available for other applications. If unneeded pages are not returned to the expanded memory manager, the system could run out of expanded memory pages or expanded memory handles. F) Terminate and stay resident programs (TSRs) should always save the state of the map registers before changing them. Since TSRs may interrupt other programs which may be using expanded memory, they must not change the state of the page mapping registers without first saving them. Before exiting, TSRs must restore the state of the map registers. The following sections describe the three ways to save and restore the state of the map registers. 1) Save Page Map and Restore Page Map (Functions 8 and 9). This is the simplest of the three methods. The EMM saves the map register contents in its own data structures -- the application does not need to provide extra storage locations for the mapping context. The last mapping context to be saved, under a particular handle, will be restored when a call to Restore Page Map is issued with the same handle. This method is limited to one mapping context for each handle and saves the context for only LIM standard 64K-byte page frames. 2) Get/Set Page Map (Function 15). This method requires the application to allocate space for the storage array. The EMM saves the mapping context in an array whose address is passed to the EMM. When restoring the mapping context with this method, an application passes the address of an array which contains a previously stored mapping context. This method is preferable if an application needs to do more than one save before a restore. It provides a mechanism for switching between more than one mapping context. 3) Get/Set Partial Page Map (Function 16). This method provides a way for saving a partial mapping context. It should be used when the application does not need to save the context of all mappable memory. This function also requires that the storage array be part of the application's data. G) All functions using pointers to data structures must have those data structures in memory which will not be mapped out. Functions 22 and 23 (Alter Map & Call and Alter Map & Jump) are the only exceptions. EMS 4.0 SPECIFICATIONS Page Frames The bank switched memory chunks are referred to as "page frames". These frame consist of four 16K memory blocks mapped into some of the normally unused system ROM address area, 0C0000-0EFFFF. Each 16K page is independent of the other and they can map to discrete or overlapping areas of the 8 megabyte expanded memory address area. Most cards allow selection of addresses to prevent conflict with other cards, such as hard disk controllers and other expanded memory boards. Calling the Manager Applications programs communicate with the EMM device driver directly via user interrupt 67h. All communication between the application program and the driver bypasses DOS completely. To call the driver, register AH is loaded with the number of the EMM service requested; DX is loaded with the file handle; and interrupt 67h is called. ES:DI is used to pass the address of a buffer or array if needed. On return AH contains 0 if the call was successful or an error code from 80h to 8Fh if unsuccessful. TESTING FOR THE PRESENCE OF THE EXPANDED MEMORY MANAGER Before an application program can use the Expanded Memory Manager, it must determine whether the manager is present. The two recommended methods are the "open handle" technique and the "get interrupt vector" technique. The majority of application programs can use either the "open handle" or the "get interrupt vector" method. However, if your program is a device driver or if it interrupts DOS during file system operations, you must use only the "get interrupt vector" method. Device drivers execute from within DOS and can't access the DOS file functions; programs that interrupt DOS during file operations have a similar restriction. During their interrupt processing procedures, they can't access the DOS file functions because another program may be using the system. Since the "get interrupt vector" method doesn't require the DOS file functions, you must use it for programs of this type. The "Open Handle" Method Most application programs can use the DOS "Open Handle" method to test for the presence of the EMM. To use this method, follow these steps in order: 1) Issue an "open handle" command (DOS function 3Dh) in "read only" access mode (register AL = 0). This function requires your program to point to an ASCII string which contains the path name of the file or device in which you're interested (register set DS:DX contains the pointer). In this case the file is actually the reserved name of the expanded memory manager. you should format the ASCII string as follows: ASCII_device_name DB 'EMMXXXX0', 0 The ASCII codes for the capital letters EMMXXXX0 are terminated by a byte containing a value of zero. 2) If DOS returns no error code, skip Steps 3 and 4 and go to Step 5. If DOS returns a "Too many open files" error code, go to Step 3. If DOS returns a "File/Path not found" error code, skip Step 3 and go to Step 4. 3) If DOS returns a "Too many open files" (not enough handles) status code, your program should invoke the "open file" command before it opens any other files. This will guarantee that at least one file handle will be available to perform the function without causing this error. After the program performs the "open file" command, it should perform the test described in Step 6 and close the "file handle" (DOS function 3Eh). Don't keep the manager "open" after this status test is performed since "manager" functions are not available through DOS. Go to Step 6. 4) If DOS returns a "File/Path not found," the memory manager is not installed. If your application requires the memory manager, the user will have to reboot the system with a disk containing the memory manager and the appropriate CONFIG.SYS file before proceeding. 5) If DOS doesn't return an error status code you can assume that either a device with the name EMMXXXX0 is resident in the system, or a file with this name is on disk in the current disk drive. Go to Step 6. 6) Issue an "I/O Control for Devices" command (DOS function 44h) with a "get device information" command (register AL = 0). DOS function 44h determines whether EMMXXXX0 is a device or a file. You must use the file handle (register BX) which you obtained in Step 1 to access the "EMM" device. This function returns the "device information" in a word (register DX). Go to Step 7. 7. If DOS returns any error code, you should assume that the memory manager device driver is not installed. If your application requires the memory manager, the user will have to reboot the system with a disk containing the memory manager and the appropriate CONFIG.SYS file before proceeding. 8) If DOS didn't return an error status, test the contents of bit 7 (counting from 0) of the "device information" word (register DX) the function returned. Go to Step 9. 9) If bit 7 of the "device information" word contains a zero, then EMMXXXX0 is a file, and the memory manager device driver is not present. If your application requires the memory manager, the user will have to reboot the system with a disk containing the memory manager and the appropriate CONFIG.SYS file before proceeding. If bit 7 contains a one, then EMMXXXX0 is a device. Go to Step 10. 10) Issue an "I/O Control for Devices" command (DOS function 44h) with a "get output status" command (register AL = 7). You must use the file handle you obtained in Step 1 to access the "EMM" device (register BX). Go to Step 11. 11) If the expanded memory device driver is ready, the memory manager passes a status value of 0FFh in register AL. The status value is 00h if the device driver is not ready. If the memory manager device driver is "not ready" and your application requires its presence, the user will have to reboot the system with a disk containing the memory manager and the appropriate CONFIG.SYS file before proceeding. If the memory manager device driver is "ready," go to Step 12. 12) Issue a "Close File Handle" command (DOS function 3Eh) to close the expanded memory device driver. You must use the file handle you obtained in Step 1 to close the "EMM" device (register BX). The "Get Interrupt Vector" technique Any type of program can use this method to test for the presence of the EMM. Use this method (not the "Open Handle" method) if your program is a device driver or if it interrupts DOS during file system operations. Follow these steps in order: 1) Issue a "get vector" command (DOS function 35h) to obtain the contents of interrupt vector array entry number 67h (addresses 0000:019Ch thru 0000:019Fh). The memory manager uses this interrupt vector to perform all manager functions. The offset portion of this interrupt service routine address is stored in the word located at address 0000:019Ch; the segment portion is stored in the word located at address 0000:019Eh. 2) Compare the "device name field" with the contents of the ASCII string which starts at the address specified by the segment portion of the contents of interrupt vector address 67h and a fixed offset of 000Ah. If DOS loaded the memory manager at boot time this name field will have the name of the device in it. Since the memory manager is implemented as a character device driver, its program origin is 0000h. Device drivers are required to have a "device header" located at the program origin. Within the "device header" is an 8 byte "device name field." For a character mode device driver this name field is always located at offset 000Ah within the device header. The device name field contains the name of the device which DOS uses when it references the device. If the result of the "string compare" in this technique is positive, the memory manager is present. Terminate and Stay Resident (TSR) Program Cooperation: In order for TSR's to cooperate with each other and with other applications, TSRs must follow this rule: a program may only remap the DOS partition it lives in. This rule applies at all times, even when no expanded memory is present. EXPANDED MEMORY SERVICES FUNCTIONS DEFINED IN EMS 3.2 SPECIFICATION Interrupt 67h Function 40h Get Manager Status LIM Function Call 1 Returns a status code indicating whether the memory manager is present and the hardware is working correctly. entry AH 40h return AH error status: 00h, 80h, 81h, 84h note 1) upward and downward compatible with both EMS and EEMS 3.2. this call can be used only after establishing that the EMS driver is in fact present 2) uses register AX Function 41h Get Page Frame Segment LIM Function Call 2 Obtain segment address of the page frame used by the EMM. entry AH 41h return AH error status: 00h, 80h, 81h, 84h BX page frame segment address (error code 0) note 1) upward and downward compatible with both EMS and EEMS 3.2. 2) uses registers AX & BX Function 42h Get Unallocated Page Count LIM Function Call 3 Obtain total number of logical expanded memory pages present in the system and the number of those pages not already allocated. entry AH 42h return AH error status: 00h, 80h, 81h, 84h BX number of unallocated pages currently availible DX total number of pages note 1) upward and downward compatible with both EMS and EEMS 3.2. Note that EMS and EEMS 3.2 had no mechanism to return the maximum number of handles that can be allocated by programs. This is handled by the EMS 4.0 new function 54h/02h. 2) uses registers AX, BX, DX Function 43h Get Handle and Allocate Memory LIM Function Call 4 Notifies the EMM that a program will be using extended memory, obtains a handle, and allocates a certain number of logical pages of extended memory to be controlled by that handle entry AH 43h BX number of 16k logical pages requested (zero OK) return AH error status: 00h, 80h, 81h, 84h, 85h, 87h, 88h, 89h DX unique EMM handle (see note 2) note 1) upward compatible with both EMS and EEMS 3.2; EMS and EEMS 3.2 do not allow the allocation of zero pages (returns error status 89h). EMS 4.0 does allow zero pages to be requested for a handle, allocating pages later using function 51h 2) your program must use this EMM handle as a parameter in any function that requires it. You can use up to 255 handles. The uppermost byte of the handle will be zero and cannot be used by the application. 3) regs AX & DX are used Function 44h Map Memory LIM Function Call 5 Maps one of the logical pages of expanded memory assigned to a handle onto one of the four physical pages within the EMM's page frame. entry AH 44h AL physical page to be mapped (0-3) BX the logical page to be mapped (zero through [number of pages allocated to the EMM handle - 1]). If the logical page number is 0FFFFh, the physical page specified in AL will be unmapped (made inaccessible for reading or writing). DX the EMM handle your program received from Function 4 (Allocate Pages). return AH error status: 00h, 80h, 81h, 83h, 84h, 8Ah, 8Bh note 1) downward compatible with both EMS and EEMS 3.2; EMS and EEMS 3.2 do not support unmap (logical page 0FFFFh) capability. Also, EEMS 3.2 specified there were precisely four physical pages; EMS 4.0 uses the subfunctions of function 58h to return the permitted number of physical pages. This incorporates the functionality of function 69h ("function 42") of EEMS. 2) uses register AX Function 45h Release Handle and Memory LIM Function Call 6 Deallocates the logical pages of expanded memory currently assigned to a handle and then releases the handle itself. entry AH 45h DX handle return AH error status: 00h, 80h, 81h, 83h, 84h, 86h note 1) upward and downward compatible with both EMS and EEMS 3.2. 2) uses register AX 3) when a handle is deallocated, its name is set to all ASCII nulls (binary zeros). 4) a program must perform this function before it exits to DOS or no other programs can use these pages or the EMM handle. Function 46h Get EMM Version LIM Function Call 7 Returns the version number of the Expanded Memory Manager software. entry AH 46h return AH error status: 00h, 80h, 81h, 84h AL version number byte (if AL=00h) binary coded decimal (BCD) format if version byte: high nibble: integer digit of the version number low nibble : fractional digit of version number i.e., version 4.0 is represented like this: 0100 0000 / \ 4 . 0 note 1) upward and downward compatible with both EMS and EEMS 3.2. It appears that the intended use for this function is to return the version of the vendor implementation of the expanded memory manager instead of the specification version. 2) uses register AX Function 47h Save Mapping Context LIM Function Call 8 Save the contents of the expanded memory page-mapping registers on the expanded memory boards, associating those contents with a specific EMM handle. entry AH 47h DX caller's EMM handle (NOT current EMM handle) return AH error status: 00h, 80h, 81h, 83h, 84h, 8Ch, 8Dh note 1) upward and downward compatible with both EMS and EEMS 3.2. 2) This only saves the context saved in EMS 3.2 specification; if a driver, interrupt routine or TSR needs to do more, functions 4Eh (Page Map functions) or 4Fh (Partial Page Map functions) should be used. 3) no mention is made about the number of save contexts to provide. AST recommends in their Rampage AT manual one save context for each handle plus one per possible interrupt (5 + <handles>). 4) uses register AX 5) this function saves the state of the map registers for only the 64K page frame defined in versions 3.x of the LIM. Since all applications written to LIM versions 3.x require saving the map register state of only this 64K page frame, saving the entire mapping state for a large number of mappable pages would be inefficient use of memory. Applications that use a mappable memory region outside the LIM 3.x page frame should use functions 15 or 16 to save and restore the state of the map registers. Function 48h Restore Page Map LIM Function Call 9 Restores the contents of all expanded memory hardwere page-mapping registers to the values associated with the given handle by a previous function 08h (Save Mapping Context). entry AH 48h DX caller's EMM handle (NOT current EMM handle) return AH error status: 00h, 80h, 81h, 83h, 84h, 8Eh note 1) upward and downward compatible with both EMS and EEMS 3.2. 2) This only restores the context saved in EMS 3.2 specification; if a driver, interrupt routine or TSR needs to do more, functions 4Eh (Page Map functions) or 4Fh (Partial Page Map functions) should be used. 3) uses register AX 4) this function saves the state of the map registers for only the 64K page frame defined in versions 3.x of the LIM. Since all applications written to LIM versions 3.x require saving the map register state of only this 64K page frame, saving the entire mapping state for a large number of mappable pages would be inefficient use of memory. Applications that use a mappable memory region outside the LIM 3.x page frame should use functions 15 or 16 to save and restore the state of the map registers. Function 49h Reserved LIM Function Call 10 This function was used in EMS 3.0, but was no longer documented in EMS 3.2. It formerly returned the page mapping register I/O port array. Use of this function is discouraged, and in EMS 4.0 may conflict with the use of the new functions 16 through 30 (4Fh through 5Dh) and functions 10 and 11. Functions 10 and 11 are specific to the hardware on Intel expanded memory boards and may not work correctly on all vendors' expanded memory boards. Function 4Ah Reserved LIM Function Call 11 This function was used in EMS 3.0, but was no longer documented in EMS 3.2. It was formerly Get Page Translation Array. Use of this function is discouraged, and in EMS 4.0 may conflict with the use of the new functions (4Fh through 5Dh). Function 4Bh Get Number of EMM Handles LIM Function Call 12 The Get Handle Count function returns the number of open EMM handles (including the operating system handle 0) in the system. entry AH 4Bh return AH error status: 00h, 80h, 81h, 84h BX handle count (AH=00h) (including the operating system handle [0]). max 255. note 1) upward and downward compatible with EMS and EEMS 3.2. 2) uses registers AX and BX Function 4Ch Get Pages Owned by Handle LIM Function Call 13 Returns number of logical expanded memory pages allocated to a specific EMM handle. entry AH 4Ch DX handle return AH error status: 00h, 80h, 81h, 83h, 84h BX pages allocated to handle, max 2048 because the EMM allows a maximum of 2048 pages (32M bytes) of expanded memory. note 1) This function is upward compatible with EMS and EEMS 3.2. 2) programmers should compare the number returned in BX with the maximum number of pages returned by function 42h register DX, total number of EMM pages. This should be an UNSIGNED comparison, just in case the spec writers decide to use 16 bit unsigned numbers (for a maximum space of one gigabyte) instead of signed numbers (for a maximum space of 512 megabytes). Unsigned comparisons will work properly in either case 3) uses registers AX and BX Function 4Dh Get Pages for All Handles LIM Function Call 14 Returns an array containing all active handles and the number of logical expanded memory pages associated with each handle. entry AH 4Dh ES:DI pointer to 1020 byte array to receive information on an array of structures where a copy of all open EMM handles and the number of pages allocated to each will be stored. return AH error status: 00h, 80h, 81h, 84h BX number of active handles (1-255); array filled with 2-word entries, consisting of a handle and the number of pages allocated to that handle. (including the operating system handle [0]). BX cannot be zero because the operating system handle is always active and cannot be deallocated. note 1) NOT COMPATIBLE with EMS or EEMS 3.2, since the new special OS handle 0000h is returned as part of the array. Unless benign use of this information is used (such as displaying the handle and count of pages associated with the handle) code should be changed to only work with handles between 01h and FFh and to specifically ignore handle 00h. 2) The array consists of an array of 255 elements. The first word of each element is the handle number, the second word contains the number of pages allocated. 3) There are two types of handles, "standard" and "raw". The specification does not talk about how this function works when both raw and standard handles exist in a given system. There is no currently known way to differentiate between a standard handle and a raw handle in EMS 4.0. 4) uses registers AX and BX Function 4Eh Get or Set Page Map LIM Function Call 15 Gets or sets the contents of the EMS page-mapping registers on the expanded memory boards. This group of four subfunctions is provided for context switching required by operating environments and systems. These functions are upward and downward compatible with both EMS and EEMS 3.2; in addition, these functions now include the functionality of EEMS function 6Ah ("function 43") involving all pages. The size and contents of the map register array will vary from system to system based on hardware vendor, software vendor, number of boards and the capacity of each board in the system. Note the array size can be determined by function 4Eh/03h. Use these functions (except for 03h) instead of Functions 8 and 9 if you need to save or restore the mapping context but don't want (or have) to use a handle. 00h Get Page Map This call saves the mapping context for all mappable memory regions (conventional and expanded) by copying the contents of the mapping registers from each expanded memory board to a destination array. The application must pass a pointer to the destination array. entry AH 4Eh AL 00h ES:DI pointer to target array return AH error status: 00h, 80h, 81h, 84h, 8Fh note 1) uses register AX 2) does not use an EMM handle 01h Set Page Map This call the mapping context for all mappable memory regions (conventional and expanded) by copying the contents of a source array into the mapping registers on each expanded memory board in the system. The application must pass a pointer to the source array. entry AH 4Eh AL 01h DS:SI pointer to source array return AH error status: 00h, 80h, 81h, 84h, 8Fh, 0A3h note 1) uses register AX 2) does not use an EMM handle 02h Get & Set Page Map This call simultaneously saves the current mapping context and restores a previous mapping context for all mappable memory regions (both conventional and expanded). It first copies the contents of the mapping registers from each expanded memory board in the system into a destination array. Then the subfunction copies the contents of a source array into the mapping registers on each of the expanded memory boards. entry AH 4Eh AL 02h DS:SI pointer to source array ES:DI pointer to target array return AH error status: 00h, 80h, 81h, 84h, 8Fh, 0A3h note 1) uses register AX 03h Get Size of Page Map Save Array entry AH 4Eh AL 03h return AH error status: 00h, 80h, 81h, 84h, 8Fh AL size in bytes of array note 1) this subfunction does not require an EMM handle 2) uses register AX FUNCTIONS NEW TO EMS 4.0 Function 4Eh Get or Set Page Map LIM Function Call 16 entry AH 4Eh AL 00h if getting mapping registers 01h if setting mapping registers 02h if getting and setting mapping registers at once 03h if getting size of page-mapping array DS:SI pointer to array holding information (AL=01/02) ES:DI pointer to array to receive information (AL=00/02) return AH error status: 00h, 80h, 81h, 84h, 8Fh, 0A3h note 1) this function was designed to be used by multitasking operating systems and should not ordinarily be used by appplication software. Function 4Fh Get/Set Partial Page Map LIM Function Call 16 These four subfunctions are provided for context switching required by interrupt routines, operating environments and systems. This set of functions provides extended functionality over the EEMS function 6Ah (function 43) involving subsets of pages. In EEMS, a subset of pages could be specified by starting position and number of pages; in this function a list of pages is specified, which need not be contiguous. Interrupt routines can use this function in place of functions 47h and 48h, especially if the interrupt routine wants to use more than the standard four physical pages. AH 4Fh AL subfunction 00h get partial page map DS:SI pointer to structure containing list of segments whose mapping contexts are to be saved ES:DI pointer to array to receive page map 01h set partial page map DS:SI pointer to structure containing saved partial page map 02h get size of partial page map BX number of mappable segments in the partial map to be saved return AH error status (00h): 00h, 80h, 81h, 84h, 8Bh, 8Fh, 0A3h error status (01h): 00h, 80h, 81h, 84h, 8Fh, 0A3h error status (02h): 00h, 80h, 81h, 84h, 8Bh, 8Fh AL size of partial page map for subfunction 02h DS:SI (call 00h) pointer to array containing the partial mapping context and any additional information necessary to restore this context to its original state when the program invokes a Set subfunction. note uses register AX Function 50h Map/Unmap Multiple Pages LIM Function Call 17 entry AH 50h AL 00h (by physical page) 01h (by segment number) CX contains the number of entries in the array. For example, if the array contained four pages to map or unmap, then CX would contain 4. DX handle DS:SI pointer to an array of structures that contains the information necessary to map the desired pages. return AH error status: 00h, 80h, 81h, 83h, 84h, 8Ah, 8Bh, 8Fh note 1) New function permits multiple logical-to-physical assignments to be made in a single call.(faster than mapping individual pages) 2) The source map array is an array of word pairs. The first word of a pair contains the logical page to map (0FFFFh if the physical page is to be totally unmapped) and the second word of a pair contains the physical page number (subfunction 00h) or the segment selector (subfunction 01h) of the physical page in which the logical page shall be mapped. 3) A map of available physical pages (by physical page number and segment selectors) can be obtained using function 58h/00h, Get Mappable Physical Address Array. 4) uses register AX 5) Both mapping and unmapping pages can be done simultaneously. 6) If a request to map or unmap zero pages is made, nothing is done and no error is returned. 7) Pages can be mapped or unmapped using one of two methods. Both methods produce identical results. A) A logical page and a physical page at which the logical page is to be mapped. This method is an extension of Function 5 (Map Handle Page). B) Specifys both a logical page and a corresponding segment address at which the logical page is to be mapped. While functionally the same as the first method, it may be easier to use the actual segment address of a physical page than to use a number which only represents its location. The memory manager verifies whether the specified segment address falls on the boundary of a mappable physical page. The manager then translates the segment address passed to it into the necessary internal representation to map the pages. Function 51h Reallocate pages LIM Function Call 18 This function allows an application to change the number of logical pages allocated to an EMM handle. entry AH 51h BX number of pages desired at return DX handle return AH error status: 00h, 80h, 81h, 83h, 84h, 87h, 88h BX number of pages now associated with handle note 1) uses registers AX, BX 2) Logical pages which were originally allocated with Function 4 are called pages and are 16K bytes long. Logical pages which were allocated with Function 27 are called raw pages and might not be the same size as pages allocated with Function 4. 3) If the status returned in BX is not zero, the value in BX is equal to the number of pages allocated to the handle prior to calling this function. This information can be used to verify that the request generated the expected results. Function 52h Get/Set Handle Attributes LIM Function Call 19 entry AH 52h AL subfunction 00h get handle attributes 01h set handle attributes BL new attribute 00h make handle volatile 01h make handle non-volatile 02h get attribute capability DX handle return AH error status: (function 00h) 00h, 80h, 81h, 83h, 84h, 8Fh, 91h error status: (function 01h) 00h, 80h, 81h, 83h, 84h, 8Fh, 90h, 91h error status: (function 02h) 00h, 80h, 81h, 84h, 8Fh AL attribute (for subfunction 00h) 00h handle is volatile 01h handle is nonvolatile AL attribute capability (for subfunction 02h) 00h only volatile handles supported 01h both volatile and non-volatile supported note 1) uses register AX 2) A volatile handle attribute instructs the memory manager to deallocate both the handle and the pages allocated to it after a warm boot. If all handles have the volatile attribute (default) at warm boot the handle directory will be empty and all expanded memory will be initialized to zero immediately after a warm boot. 3) If the handle's attribute has been set to non-volatile, the handle, its name (if it is assigned one), and the contents of the pages allocated to the handle are all maintained after a warm boot. 4) Most PCs disable RAM refresh signals for a considerable period during a warm boot. This can corrupt some of the data in memory boards. Non- volatile handles should not be used unless it is definitely known that the EMS board will retain proper function through a warm boot. 5) subfunction 02h can be used to determine whether the memory manager can support the non-volatile attribute. 6) Currently the only attribute supported is non-volatile handles and pages, indicated by the least significant bit. Function 53h Handle Name Functions LIM Function Call 20 EMS handles may be named. Each name may be any eight characters. At installation, all handles have their name initialized to ASCII nulls (binary zeros). There is no restriction on the characters which may be used in the handle name (ASCII chars 00h through 0FFh). A name of eight nulls (zeroes) is special, and indicates a handle has no name. Nulls have no special significance, and they can appear in the middle of a name. The handle name is 64 bits of binary information to the EMM. Functions 53h and 54h provide a way of setting and reading the names associated with a particular handle. Function 53h manipulates names by number. When a handle is assigned a name, at least one character in the name must be a non-null character in order to distinguish it from a handle without a name. 00h Get Handle Name This subfunction gets the eight character name currently assigned to a handle. The handle name is initialized to ASCII nulls (binary zeros) three times: when the memory manager is installed, when a handle is allocated, and when a handle is deallocated. entry AH 53h AL 00h DX handle ES:DI pointer to 8-byte handle name array into which the name currently assigned to the handle will be copied. return AH error status: 00h, 80h, 81h, 83h, 84h, 8Fh note uses register AX 01h Set Handle Name This subfunction assigns an eight character name to a handle. A handle can be renamed at any time by setting the handle's name to a new value. When a handle is deallocated, its name is removed (set to ASCII nulls). entry AH 53h AL 01h DX handle DS:SI pointer to 8-byte handle name array that is to be assigned to the handle. The handle name must be padded with nulls if the name is less than eight characters long. return AH error status: 00h, 80h, 81h, 83h, 84h, 8Fh, 0A1h note uses register AX Function 54h Handle Directory Functions LIM Function Call 21 Function 54h manipulates handles by name. 00h Get Handle Directory Returns an array which contains all active handles and the names associated with each. entry AH 54h AL 00h ES:DI pointer to 2550 byte target array return AH error status: 00h, 80h, 81h, 84h, 8Fh AL number of active handles note 1) The name array consists of 10 byte entries; each entry has a word containing the handle number, followed by the eight byte (64 bit) name. 2) uses register AX 3) The number of bytes required by the target array is: 10 bytes * total number of handles 4) The maximum size of this array is: (10 bytes/entry) * 255 entries = 2550 bytes. 01h Search for Named Handle Searches the handle name directory for a handle with a particular name. If the named handle is found, this subfunction returns the handle number associated with the name. entry AH 54h AL 01h DS:SI pointer to an 8-byte string that contains the name of the handle being searched for return AH error status: 00h, 80h, 81h, 84h, 8Fh, A0h, 0A1h DX handle number note 1) uses registers AX and DX 02h Get Total Handles Returns the total number of handles the EMM supports, including the operating system handle (handle value 0). entry AH 54h AL 02h return AH error status: 00h, 80h, 81h, 84h, 8Fh BX total number of handles availible note 1) This is NOT the current number of handles defined, but the maximum number of handles that can be supported in the current environment. 2) uses registers AX and BX Function 55h Alter Page Map and Jump (cross page branch) LIM Function Call 22 Alters the memory mapping context and transfers control to the specified address. Analogous to the FAR JUMP in the 8086 family architecture. The memory mapping context which existed before calling function is lost. entry AH 55h AL 00h physical page numbers provided by caller 01h segment addresses provided by caller DX handle DS:SI pointer to structure containing map and jump address return AH error status: 00h, 80h, 81h, 83h, 84h, 8Ah, 8Bh, 8Fh note 1) Flags and all registers except AX are preserved across the jump. 2) uses register AX 3) Values in registers which don't contain required parameters maintain the values across the jump. The values in registers (with the exception of AX) and the flag state at the beginning of the function are still in the registers and flags when the target address is reached. 4) Mapping no pages and jumping is not considered an error. If a request to map zero pages and jump is made, control is transferred to the target address, and this function performs a far jump. Function 56h Alter Page Map and Call (cross page call) LIM Function Call 23 00h and 01h This subfunction saves the current memory mapping context, alters the specified memory mapping context, and transfers control to the specified address. entry AH 56h AL 00h physical page numbers provided by caller 01h segment addresses provided by caller DS:SI pointer to structure containing page map and call address DX handle return AH error status: 00h, 80h, 81h, 83h, 84h, 8Ah, 8Bh, 8Fh note 1) Flags and all registers except AX are preserved to the called routine. On return, flags and all registers except AX are preserved; AL is set to zero and AX is undefined. 2) uses register AX 3) Values in registers which don't contain required parameters maintain the values across the call. The values in registers (with the exception of AX) and the flag state at the beginning of the function are still in the registers and flags when the target address is reached. 4) Developers using this subfunction must make allowances for the additional stack space this subfunction will use. 02h Get Page Map Stack Space Size Since the Alter Page Map & Call function pushes additional information onto the stack, this subfunction returns the number of bytes of stack space the function requires. entry AH 56h AL 02h return: BX number of bytes of stack used per call AH error status: 00h, 80h, 81h, 84h, 8Fh note 1) if successful, the target address is called. Use a RETF to return and restore mapping context 2) uses registers AX, BX Function 57h Move/Exchange Memory Region LIM Function Call 24 00h Move Memory Region Moves data between two memory areas. Includes moves between paged and non-paged areas, or between two different paged areas. entry AH 57h AL 00h SI offset to request block DS segment selector to request block return AH error status: 00h, 80h, 81h, 83h, 84h, 8Ah, 8Fh, 92h, 93h, 94h, 95h, 96h, 98h, 0A2h note 1) uses register AX 01h Exchange Memory Region Exchanges data between two memory areas. Includes exchanges between paged and non-paged areas, or between two different paged areas. entry AH 57h AL 01h DS:SI pointer to the data structure which contains the source and destination information for the exchange. return AH error status: 00h, 80h, 81h, 83h, 84h, 8Ah, 8Fh, 93h, 94h, 95h, 96h, 97h, 98h, 0A2h note 1) The request block is a structure with the following format: dword region length in bytes byte 0=source in conventional memory 1=source in expanded memory word source handle word source offset in page or selector word source logical page (expanded) or selector (conventional) byte 0=target in conventional memory 1=target in expanded memory word target handle word target offset in page or selector word target logical page (expanded) or selector (conventional) 2) Expanded memory allocated to a handle is considered to be a linear array, starting from logical page 0 and progressing through logical page 1, 2, ... n, n+1, ... up to the last logical page in the handle. 3) uses register AX Function 58h Mappable Physical Address Array LIM Function Call 25 These functions let you obtain a complete map of the way physical memory is laid out in a vendor independent manner. This is a functional equivalent of EEMS function 68h ("function 41"). EEMS function 60h ("function 33") is a subset call of 68h. 00h Get Array Returns an array containing the segment address and physical page number for each mappable physical page in a system. This array provides a cross reference between physical page numbers and the actual segment addresses for each mappable page in the system. entry AH 58h AL 00h ES:DI pointer to target array return AH error status: 00h, 80h, 81h, 84h, 8Fh CX entries in target array note 1) The information returned is in an array composed of word pairs. The first word is the physical page's segment selector, the second word the physical page number. Note that values are not necessarily returned in a particular order, either ascending/decending segment selector values or as ascending/decending physical page number. 2) For compatibility with earlier EMS specifications, physical page zero contains the segment selector value returned by function 41h, and physical pages 1, 2 and 3 return segment selector values that corrospond to the physical 16 KB blocks immediately following physical page zero. 3) uses registers AX and CX 4) The array is sorted in ascending segment order. This does not mean that the physical page numbers associated with the segment addresses are also in ascending order. 01h Get Physical Page Address Array Entries. Returns a word which represents the number of entries in the array returned by the previous subfunction. This number also indicates the number of mappable physical pages in a system. entry AH 58h AL 01h return AH error status: 00h, 80h, 81h, 84h, 8Fh CX number of entries returned by 58h/00h note 1) multiply CX by 4 for the byte count. 2) uses registers AX and CX Function 59h Get Expanded Memory Hardware Information LIM Function Call 26 These functions return information specific to a given hardware implementation and to use of raw pages as opposed to standard pages. The intent is that only operating system code ever need use these functions. 00h Get EMS Hardware Info Returns an array containing expanded memory hardware configuration information for use by an operating system. entry AH 59h AL 00h ES:DI pointer to 10 byte target array The target array has the following format: word: raw page size in paragraphs (multiples of 16 bytes) word: number of alternate register sets word: size of page maps (function 4Eh [15]) word: number of alternate registers sets for DMA word: DMA operation -- see full specification return AH error status: 00h, 80h, 81h, 84h, 8Fh, 0A4h note 1) uses register AX 2) This function is for use by operating systems only. 3) This function can be disabled at any time by the operating system. 01h Get Unallocated Raw Page Count Returns the number of unallocated non-standard length mappable pages as well as the total number of non-standard length mappable pages of expanded memory entry AH 59h AL 01h return AH error status: 00h, 80h, 81h, 84h, 8Fh BX unallocated raw pages availible for use DX total raw 16k pages of expanded memory note 1) uses registers AX, BX, CX 2) An expanded memory page which is a sub-multiple of 16K is termed a raw page. An operating system may deal with mappable physical page sizes which are sub-multiples of 16K bytes. 3) If the expanded memory board supplies pages in exact multiples of 16K bytes, the number of pages this function returns is identical to the number Function 3 (Get Unallocated Page Count) returns. In this case, there is no difference between a page and a raw page. Function 5Ah Allocate Raw Pages LIM Function Call 27 Allocates the number of nonstandard size pages that the operating system requests and assigns a unique EMM handle to these pages. entry AH 5Ah AL 00h allocate standard pages 01h allocate raw pages BX number of pages to allocate return AH error status: 00h, 80h, 81h, 84h, 85h, 87h, 88h DX unique raw EMM handle (1-255) note 1) it is intended this call be used only by operating systems 2) uses registers AX and DX 3) For all functions using the raw handle returned in DX, the length of the physical and logical pages allocated to it are some nonstandard length (that is, not 16K bytes). 4) this call is primarily for use by operating systems or EMM drivers supporting hardware with a nonstandard EMS page size. Function 5Bh Alternate Map Register Set - DMA Registers LIM Function Call 28 entry AH 00h Get Alternate Map Register Set 01h Set Alternate Map Register Set BL new alternate map register set number ES:DI pointer to map register context save area if BL=0 02h Get Alternate Map Save Array Size 03h Allocate Alternate Map Register Set 04h Deallocate Alternate Map Register Set BL number of alternate map register set 05h Allocate DMA Register Set 06h Enable DMA on Alternate Map Register Set BL DMA register set number DL DMA channel number 07h Disable DMA on Alternate Map Register Set BL DMA register set number 08h Deallocate DMA Register Set BL DMA register set number return AH status: 00h, 02h 00h, 80h, 84h, 81h, 8Fh, 0A4h 01h 00h, 80h, 81h, 84h, 8Fh, 9Ah, 9Ch, 9Dh, 0A3h, 0A4h 03h, 05h 00h 80h 81h 84h, 8Fh, 9Bh, 0A4h 04h 00h, 80h, 81h, 84h, 8Fh, 9Ch, 9Dh, 0A4h 06h, 07h 00h, 80h, 81h, 84h, 8Fh, 9Ah, 9Ch, 9Dh, 9Eh, 9Fh, 0A4h BL current active alternate map register set number if nonzero (AL=0) BL number of alternate map register set; zero if not supported (AL=3) DX array size in bytes (subfunction 02h) ES:DI pointer to a map register context save area if BL=0 (AL=0) note 1) this call is for use by operating systems only, and can be enabled or disabled at any time by the operating system 2) This set of functions performs the same functions at EEMS function 6Ah subfunctions 04h and 05h ("function 43"). 3) 00h uses registers AX, BX, ES:DI 01h uses register AX 02h uses registers AX and DX 03h uses registers AX and BX 04h uses register AX 05h uses registers AX, BX 06h uses register AX 07h uses register AX Function 5Ch Prepare EMS Hardware for Warm Boot LIM Function Call 29 Prepares the EMM hardware for a warm boot. entry AH 5Ch return AH error status: 00h, 80h, 81h, 84h note 1) uses register AX 2) this function assumes that the next operation that the operating system performs is a warm boot of the system. 3) in general, this function will affect the current mapping context, the alternate register set in use, and any other expanded memory hardware dependencies which need to be initialized at boot time. 4) if an application decides to map memory below 640K, the application must trap all possible conditions leading to a warm boot and invoke this function before performing the warm boot itself. Function 5Dh Enable/Disable OS Function Set Functions LIM Function Call 30 Lets the OS allow other programs or device drivers to use the OS specific functions. This capability is provided only for an OS which manages regions of mappable conventional memory and cannot permit programs to use any of the functions which affect that memory, but must be able to use these functions itself. entry AH 5Dh AL 00h enable OS function set 01h disable OS function set 02h return access key (resets memory manager, returns access key at next invocation) BX,CX access key returned by first invocation return BX,CX access key, returned only on first invocation of function AH status 00h, 80h, 81h, 84h, 8Fh, 0A4h note 1) this function is for use by operating systems only. The operating system can disable this function at any time. 2) 00h uses registers AX, BX, CX 01h uses registers AX, BX, CX 02h uses register AX 3) 00h, 01h: The OS/E (Operating System/Environment) functions these subfunctions affect are: Function 26. Get Expanded Memory Hardware Information. Function 28. Alternate Map Register Sets. Function 30. Enable/Disable Operating System Functions. Function 5Eh Unknown LIM Function call (not defined under LIM) Function 5Fh Unknown LIM Function call (not defined under LIM) Function 60h EEMS - Get Physical Window Array LIM Function call (not defined under LIM) entry AH 60h ES:DI pointer to buffer return AH status AL number of entries buffer at ES:DI filled Function 61h Generic Accelerator Card Support LIM Function Call 34 Contact AST Research for a copy of the Generic Accelerator Card Driver (GACD) Specification note Can be used by accelerator card manufacturer to flush RAM cache, ensuring that the cache accurately reflects what the processor would see without the cache. Function 68h EEMS - Get Addresses of All Page Frames in System LIM Function Call (not defined under LIM) entry AH 68h ES:DI pointer to buffer return AH status AL number of entries buffer at ES:DI filled note Equivalent to LIM 4.0 function 58h Function 69h EEMS - Map Page Into Frame LIM Function Call (not defined under LIM) entry AH 69h AL frame number BX page number DX handle return AH status note Similar to EMS function 44h Function 6Ah EEMS - Page Mapping LIM Function Call (not defined under LIM) entry AH 6Ah AL 00h save partial page map CH first page frame CL number of frames ES:DI pointer to buffer which is to be filled 01h restore partial page map CH first page frame CL number of frames DI:SI pointer to previously saved page map 02h save and restore partial page map CH first page frame CL number of frames ES:DI buffer for current page map DI:SI new page map 03h get size of save array CH first page frame CL number of frames return AL size of array in bytes 04h switch to standard map register setting 05h switch to alternate map register setting 06h deallocate pages mapped to frames in conventional memory CH first page frame CL number of frames return AH status note Similar to LIM function 4Eh, except that a subrange of pages can be specified EXPANDED MEMORY MANAGER ERROR CODES EMM error codes are returned in AH after a call to the EMM (int 67h). code meaning 00h function successful 80h internal error in EMM software (possibly corrupted driver) 81h hardware malfunction 82h EMM busy (dropped in EEMS 3.2) 83h invalid EMM handle 84h function requested not defined - unknown function code in AH. 85h no more EMM handles availible 86h error in save or restore of mapping context 87h more pages requested than exist 88h allocation request specified more logical pages than currently availible in system (request does not exceed actual physical number of pages, but some are already allocated to other handles); no pages allocated 89h zero pages; cannot be allocated (dropped in EMS 4.0) 8Ah logical page requested to be mapped outside range of logical pages assigned to handle 8Bh illegal page number in mapping request (valid numbers are 0 to 3) 8Ch page-mapping hardware state save area full 8Dh save of mapping context failed; save area already contains context associated with page handle 8Eh retore of mapping context failed; save area does not contain context for requested handle 8Fh subfunction parameter not defined (unknown function) LIM 4.0 extended error codes: 90h attribute type undefined 91h warm boot data save not implemented 92h move overlaps memory 93h move/exchange larger than allocated region 94h conventional/expanded regions overlap 95h logical page offset outside of logical page 96h region larger than 1 MB 97h exchange source/destination overlap 98h source/destination undefined or not supported 99h (no status assigned) 9Ah alternate map register sets supported, specified set is not 9Bh all alternate map & DMA register sets allocated 9Ch alternate map & DMA register sets not supported 9Dh alternate map register or DMA set not defined, allocated or is currently defined set 9Eh dedicated DMA channels not supported 9Fh dedicated DMA channels supported; specifed channel is not 0A0h named handle could not be found 0A1h handle name already exists 0A2h move/exchange wraps around 1 MB boundry 0A3h data structure contains corrupted data 0A4h access denied