Assuming the main memory and L2 cache are fine, have you tried setting L1 cache to Write-Through instead of Write-Back? Some 486 motherboards have very problematic WB cache implementations...

Also, do the games run fine with other CPUs in the same board?

TheMobRules wrote:

Assuming the main memory and L2 cache are fine, have you tried setting L1 cache to Write-Through instead of Write-Back? Some 486 motherboards have very problematic WB cache implementations...

Also, do the games run fine with other CPUs in the same board?

According to CHKCPU the L1 cache is already in write-through mode. CACHECHK gave me no errors, so I guess L2 cache is fine, too. How can I check RAM?

Going to try 486DX2@66 tomorrow.

Tried running AIDA16 — at Memory Specification it shows that DPMI and DPMS are "not supported". Aren't those the modes that are used by protected mode games?

Have you tried running the system without optional devices?
- Try booting in safe mode (Press SHIFT when the message 'MS-DOS is starting ...' appears). Safe-mode will skip the configuration in CONFIG.SYS and AUTOEXEC.BAT.
- Try removing the AWE32 (ánd run MS-DOS in safe mode).
- Try running with one SIMM (and switch them if the problem still occurs).

I think the jumper settings are wrong, as none of my 4 pci motherboards have the same settings for the Cyrix 5x86 vs the settings for Intel/Amd.

meljor wrote:

I think the jumper settings are wrong, as none of my 4 pci motherboards have the same settings for the Cyrix 5x86 vs the settings for Intel/Amd.

How do I tell if they are correct? I don't think this motherboard has explicit support for 5x86

I would start with an Intel DX2-66 (write-thru) and jumper accordingly. This was probably the most compatible CPU.

So I ended up trying a DX4-100 CPU. The system started, but the games still wouldn't work. After that I've tried changing 2x8MB FPM modules for 4x4MB and that actually did the trick. Not sure why, though. I definitely went through several 8MB RAM modules on this system, so maybe it specifically didn't like the 2x8 configuration?

Did you try several brands of 8 MB FPM sticks? I have found that, for whatever reasons, some boards do not like certain brands of RAM, whereby different brands of the same internal memory arrangement would work. This seems particularly true of 486 boards in my experience.

Yeah, I tried different sticks. However, I was too quick to consider this issue solved. Now my computer can freeze or reboot 5-10 minutes into the game. I've seen that in Doom and Street Rod 2. I'll recheck the jumpers tomorrow, but the benchmarks showed that DX4-100 works as it should.

sounds like a configuration issue. Try this:

- set cache timings in bios to their highest values
- check cache chips - they should be -15 chips. -20 ones can cause problems with faster CPUs
- disable external cache in bios (will be slow) but it's for diagnostic purposes. If your machine is stable like this, you might have a problematic cache chip.
- check memory timings - set them to their highest values
- check jumper settings on the board - specifically write back / write trough settings
- check CPU voltage. Make sure it's at 3.3/3.45 volts. Most CPUs don't like it when you over-volt them too much
- check BIOS settings for L2 cache WB/WT modes
- clean memory slots and ram sticks with contact cleaner (carefully).

Hope any of the above help.