beugel@cs.vu.nl (Beugel BJ) (06/10/88)
I am having a very strange and annoying problem with my XT while doing disk I/O with large files in certain programs. Any help will be much appreciated. Please mail me any answers rather than posting them. My system is configured as follows: One IMC PC/XT with - 4.77/8 MHz (Turbo) NEC V20 CPU; - 640 K, 150 ns, parity checked main memory; - 2 x 360 K floppy drives; - 20 M, 65 ms Tandon hard-disk TM 262 with 3 sectors interleave; - Western Digital WD 1002A-WX1 hard-disk controller; - Hercules compatible display adapter with 1 parallel printer port; - Multi I/O card; - ANTEX BIOS; - DOS 3.1 The problem is as follows: In slow 4.77 MHz mode I have no problems whatsoever. In 8 Mhz turbo mode however, the system hangs when I try to save or copy a large file (e.g. 140 K) on the hard-disk from within WordPerfect. The screen is cleared except for an error message saying "PARITY CHECK 200000 (S)" which is obviously not a WordPerfect message but a BIOS message. After this the system hangs completely. Even Ctrl-Alt-Del won't work. Sometimes the system hangs without showing any error message. My WordPerfect makes a backup of the file being edited every 15 minutes and this also hangs the system. While copying files on the hard-disk with the DOS COPY-command I have no problems. Another program that hangs the system in exactly the same way is PK(X)ARC. It hangs the system while archiving or extracting large files on the hard-disks. Both WP and PK(X)ARC seem to have no problems with small files. Saving, copying, extracting and archiving files on one of the floppy drives works fine too. I have a program to test memory and my memory passes all the tests both in slow and turbo mode. I pulled out the memory chip that stores the parity bits of the lower 256 K which resulted in the above mentioned error message when I booted the computer. When I pull out the same chip for the next 256 K the system boots fine but when I run the memory test the message "PARITY CHECK 240000 (S)" appears. Obviously the message will only appear when the corresponding memory is being addressed. I exchanged all the chips for the lower 256 K with the ones for the next 256 K but nothing changed. If anyone has any ideas or suggestions please let me know. Thanks in advance, Berend Jan Beugel (beugel@cs.vu.nl via mcvax). Bye bye!
chan@encore.UUCP (Jerry Chan) (06/12/88)
In article <1050@klipper.cs.vu.nl> beugel@cs.vu.nl (Beugel BJ) writes: >- 640 K, 150 ns, parity checked main memory; >The problem is as follows: > >In slow 4.77 MHz mode I have no problems whatsoever. >In 8 Mhz turbo mode however, the system hangs when I >try to save or copy a large file (e.g. 140 K) on the >hard-disk from within WordPerfect. >The screen is cleared except for an error message >saying "PARITY CHECK 200000 (S)" which is obviously not a You've got to be careful when using 150nsec parts while running 0 wait states at 8mhz. You really should be using 120's to be safe. Year(s) ago, when memory was bountiful and cheap, lots of Japanese chips were used; nowadays, Japanese chips are hard to come by, and as a result, American chips are used. It turns out, in my experience, that the margins on the Japanese parts tend to be much better than the American counterparts, i.e., 120nsec NEC's work where the same TI parts fail. The problem comes when the systems integrators try to substitute the "slower" American chips for the Japanese counter- parts. Should work, but experience has shown otherwise. The problem with marginal memory chips is that it is extremely difficult to isolate the problem -- the system may fail lots of different ways. Ways to find out: (1) Substitute chips with faster ones (laughter and jeering in background -- $$$); (2) Run your system at a slower clock; (3) run your system with an added wait state (jumper on motherboard, keyboard combo, ...). If your system works when in any of these other modes, the ram can be considered suspect. One more thing -- this would help provide further insight to find the problem: is your system new? Has it ever been able to run the programs which now fail? If it was able to run the mentioned programs, what is different now than before (hardware, software)? You may want to back off on any changes you'd made to the system to see if the problem goes away. Hope this helps -- +----------------+ Jerry H. Chan linus--+ +--+-------------+ | Encore Computer Corp. necntc--| | | E n c o r e | | 257 Cedar Hill St. ihnp4--+-encore!chan | +-------------+--+ Marlboro MA 01752 decvax--| +----------------+ (617) 460-0500 talcott--+