Simtel MSDOS 1992 June

home *** CD-ROM | disk | FTP | other *** search

/ Simtel MSDOS 1992 June / SIMTEL_0692.cdr / msdos / sysutl / ramtest.arc / RAMTEST.DOC < prev next >

Wrap

Text File | 1986-04-02 | 12.2 KB | 380 lines

RAMTEST Page 1 WARNING ------- Executing this program WILL destroy the contents of memory, in- cluding RAM disks! Now that you've been warned, I think you will find this program useful, not only in identifying an existing fault, but also as part of a periodic maintainence program. This program has been developed as an exhaustive test of an IBM PC's system RAM. It is much more comprehensive than the PC Power On Self Test (POST) and delivers diagnostic messages which are much easier to understand. There are two different versions of the test. RAMTEST.COM is the test which should be used with the IBM PC and compatibles. Note that it requires a fair amount of hardware compatibility to work properly. Users of computers which do not make use of parity checked memory (such as the Eagle PC) or who experience dif- ficulty during PASS 2 of the test should install the patch given in the Hardware Requirements section. RAMTESTA.COM is the version to be used on the IBM PCAT. The documentation for both versions is identical. For more informa- tion on the required hardware compatibility, see page 3 of this document. To start the test, just type RAMTEST at the DOS prompt. There are no additional parameters. This test is best run from a floppy disk which has been formatted using the /S option and contains no other RAM-based utilities. Some of the commonly available memory-resident utilities (for ex- ample, SideKick from BORLAND) 'take command' of the system and will cause RAMTEST to crash. RAMTEST functions in several distinct phases. After signing-on, RAMTEST starts searching for the top of contiguous memory. This search is performed by examining RAM and not by consulting the system configuration switches. Once the top of memory is found, the actual testing portion of the program is relocated and test- ing begins. RAM is tested beginning with address 0:500 and continues up to but not including the top 32k of the contiguous RAM below screen memory. These limits were chosen for the following reasons. 1) BIOS uses RAM below 0:500 for scratch area and RAMTEST uses BIOS exclusively for screen I/O. 2) The testing program needs a place to live undisturbed. RAM is tested in 32k blocks. The pattern for the test is taken from the BIOS ROMs. Randomness is added by use of iteration count to modify the data. During PASS 1, each RAM location is modified and then verified. This insures that each location can be ac- curately written to and read from. During PASS 2, each location Copyright (c) 1986 Digital Mechanics, Inc. RAMTEST Page 2 is re-read and compared to it's reference byte in ROM and the parity bit is checked. This part of the test insures that the parity generating and checking circuitry is functioning cor- rectly, that the address decoding is working properly and that there are no locations in RAM shorted to other locations. Should no errors occur during the two passes, RAMTEST announces the successful completion of the test and prompts you to turn off the computer to stop the test. If not stopped, however, RAMTEST will start over, using a different set of patterns each time. Since some memory errors do not show up until after hours of operating time, if you're trying to track down a failure, it is suggested that you let RAMTEST run awhile, perhaps overnight. Should an error occur, RAMTEST stops immediately, displays a mes- sage identifying the error, and halts. Note that the only way to exit this condition is to turn the computer off. A typical error message is: Memory contents failure. Address = 5000:0000 Data is: 1B Data should be: 1F Turn power off, wait 5 seconds, and turn power back on. The above example shows that the failure occured on an expansion board (System memory extends to 0:FFFF on 64k motherboards, and to 3000:FFFF on 256k motherboards. The presence of 4116 RAM chips indicates a 64k motherboard.). It also shows that bit 1 was 0 when it should have been 1. In cases like this, the RAM chip in the bit 1 position is frequently at fault. The RAM chips are the most delicate components in the memory system, and the easiest to test for defects. This is because the RAM chips are socketed (ex- cept for the first 16k or 64k) and the rest of the chips such as address decoding and data buffers are rarely, if ever, socketed. The last two pages of this document diagram the location of the RAM chips on the motherboard for both 64k systems and the 256k systems. Refer to the documentation that came with your add-in memory board for instructions on locating and replacing RAM chips that make up the memory above 1000:0 (64k motherboard) or 4000:0 (256k motherboard). The failure codes which are analyzed at the top of each page refer to the code which the PC prints when an error is encoun- tered during POST. If this occurs, the code will be printed, the speaker will beep, the screen will go blank, and the computer will have to be turned off. This will all happen in the span of about one second, so watch carefully to see the error code. Copyright (c) 1986 Digital Mechanics, Inc. RAMTEST Page 3 RAMTEST is provided at no charge to the user. Feel free to share it with your friends, but please do not give away altered ver- sions or versions which have had the copyright notice removed. The essence of 'user-supported' software is to provide personal computer users with quality software without high prices, and yet to provide incentive for programmers to continue to develop new products. If you find this program useful, a contribution ($10 suggested) would be greatly appreciated. Any suggestions or com- ments you may have are also welcome. Jim Weisz Digital Mechanics, Inc. P.O. Box 1356 Lombard, Il. 60148 HARDWARE REQUIREMENTS PC NMI Enable/Disable port = 0A0H RAM parity check control port = 61H (bits 4 & 5 00xx0000) Parity status port = 62H (bits 7 & 8 xx000000) Note: Users of the Eagle PC and other compatible computers which do not use parity memory need to make the following patch using DEBUG. The patch disables parity checking which causes problems on the Eagle. (Maybe the Sperry PC also) A>DEBUG RAMTEST.COM -F 1F2 1F9 90 -F 21A 222 90 -W Writing 06A4 bytes -Q A> PCAT NMI Enable/Disable port = 70H RAM parity check control port = 61H (bits 2 & 3 0000xx00) Parity status port = 61H (bits 7 & 8 xx000000) Copyright (c) 1986 Digital Mechanics, Inc. RAMTEST Page 4 MEMORY FAILURE CODE ANALYSIS: 64k motherboard SAMPLE FAILURE CODE: 4402 201 |||| ||| |||| +++---- SYSTEM CODE - INDICATES MEMORY FAILURE ||++-------- FAILED BIT - 00 INDICATES PARITY |+---------- FAILED 16K BLOCK - 0, 4, 8, OR C +----------- FAILED 64K SEGMENT SYSTEM BOARD (Lower left corner when viewed from the front) SEGMENT = 0000 BIT FIRST 2 DIGITS OF ADDR P 0 1 2 3 4 5 6 7 ERROR CODE 0000 - 3FFF * * * * * * * * * 00 (This row is soldered in.) 4000 - 7FFF * * * * * * * * * 00 8000 - BFFF * * * * * * * * * 00 C000 - FFFF * * * * * * * * * 00 SECOND 2 DIGITS OF 00 01 02 04 08 10 20 40 80 ERROR CODE Copyright (c) 1986 Digital Mechanics, Inc. RAMTEST Page 5 MEMORY FAILURE CODE ANALYSIS: 256k motherboard SAMPLE FAILURE CODE: 4402 201 |||| ||| |||| +++---- SYSTEM CODE - INDICATES MEMORY FAILURE ||++-------- FAILED BIT - 00 INDICATES PARITY |+---------- FAILED 16K BLOCK - 0, 4, 8, OR C +----------- FAILED 64K SEGMENT SYSTEM BOARD (Lower left corner when viewed from the front) BIT FIRST 2 DIGITS OF SEGMENT P 0 1 2 3 4 5 6 7 ERROR CODE 0000 * * * * * * * * * 0x (This row is soldered in.) 1000 * * * * * * * * * 1x 2000 * * * * * * * * * 2x 3000 * * * * * * * * * 3x SECOND 2 DIGITS OF 00 01 02 04 08 10 20 40 80 ERROR CODE Copyright (c) 1986 Digital Mechanics, Inc. Version 2 addendum Version 2 of RAMTEST corrects an error which occurs when the test is run on a compatible machine. Briefly, the pattern which was written to memory came from the top 32k of the IBM PC ROMs. Compatibles almost invariably do not have that much ROM, so the pattern was being generated from non-existant memory. On the second pass, a different value was obtained and resulted in a memory contents error. This has been corrected by using a random number generator instead. The memory contents error message has been changed slightly so as to be more understandable. The new format is: Memory contents failure. Address = 5000:0000 76543210 Bit # Data is: 00011011 Data should be: 00011111 Turn power off, wait 5 seconds, and turn power back on. As you can see, the offending bit is more easily recognized by comparing the two data patterns. In this example, the RAM chip occupying the bit 2 position is probably bad. As a note, if more than one bit is different, the RAM chips are probably not at fault, although it is possible. To further explain the failure address, the following chart contains the addresses contained in the first 4 rows of memory on 64k, 256k, and popular 640k motherboards. 64k 256k 640k 0000:0000 - 0000:3FFF 0000:0000 - 0000:FFFF 0000:0000 - 3000:FFFF 0000:4000 - 0000:7FFF 1000:0000 - 1000:FFFF 4000:0000 - 7000:FFFF 0000:8000 - 0000:BFFF 2000:0000 - 2000:FFFF 8000:0000 - 8000:FFFF 0000:C000 - 0000:FFFF 3000:0000 - 3000:FFFF 9000:0000 - 9000:FFFF I hope this additional information is helpful. With any luck, 'Version 3' of this program will have much better diagnostics and may even be published. Thanks for your support.