Memory upgrade problems
Posted on 1997-10-04
I just purchased 4 additional SIMM 4 Mb 30-pin memory to my 486 computer. I previously had 16 Mb installed (4x4 Mb SIMM).
When I had installed them the BIOS found all 32 Mbytes.
Though, during booting Windows95 the computer restarts after few seconds. I also tried using Windows NT, but this failed in the same mannor.
I was able to get the computer to boot MS-DOS without loading EMM386.EXE. Thereafter I used a test program from AMI called AMIDIAG to see if it could detect any problems.
This program failed at the cache memory test. It counts up from 0 Mb to 16 Mb (0ffffffh) without any problems. At the address 1000000h it reboots without any notice.
1) I tested with different memory cards for the upper 16 Mb memory.
2) I tried switching to an identical motherboard.
3) I changed the video card from an accelerator card to an old TsengLab.
4) I tried with all add-on cards but the TsengLab video card and the floppy disk controller removed.
All these actions did not solve the problem.
Now I changed some parameters in the BIOS settings.
When disabling the cache memory for the upper 16 Mbytes the computer was able to boot both Windows95 and Windows NT, though it was slower than it was with the *old* configuration :).
This is the status of the problem today.
Motherboards: 80486 CAM/33-U0 (M418U00) and 80486 CAM/50-U0 (M41AU00)
(Both specified to handle up to 32 Mb RAM)
Chipset: 82C206, 82C481A and 82C482AF
Cache: 256kb 8 pcs 32k x 8 chip SRAM (Type:dt71256 S25TP)
3 pcs 16k x 4 chip Tag RAM (Type:WS22B65AK-15)
BIOS: AMI 40-0100-B81105-00101111-070791-UMC480A-F (date 03/16/1992)
Q1. Does anyone recognize who the motherboard manufacturer is?
Q2. What settings in the BIOS should be changed to make the computer able to run properly without disabling the cache memory for the upper 16 Mbytes of memory?
Q3. Do I really have 256k cache memory? My BIOS detects 256k and the motherboard is strapped for 256k cache.
Thanks for any answers!!