How old is the PSU? Have you tried checking the rails with a multimeter?

First you should set BIOS settings for memory and cache timings to slow and go from there.

Well, I do have a LOT of things plugged into the PSU - 2 hard disks, 2 floppies, a zip drive, a tape backup, and a CDROM. However, they're not generally being used.

PSU is probably original.

As far as I know, the RAM timing is at the slowest possible settings (1 WS, etc) - I'll snap a pic of the screen when I get home.

Unplug the power to anything you don't need for testing stability. See if it makes a difference.

Did you try a regular 386 CPU? Sounds like typical Cyrix cache trouble.

I've retarded all the wait states to the slowest possible values and removed ALL shadowing. Still unstable.

I will try another CPU I have an AM386DX40 lying around (several I think).

Also, once in a blue moon when the system starts, it causes the EMM386 to crash on boot (config.sys) and it spews a bunch of memory locations. I've replaced the RAM, so unless ALL my RAM is bad somehow, I think maybe it is the motherboard... It seems to me that the longer the computer is on (or else gets warm), the more unstable it is.

I will also try to unplug the redundant drives, however I believe my motherboard (which has a card in almost every slot) sucks up a lot of power running the video card (Mach32) and the AHA 1542 SCSI controller (and its loud, likely power hungry drive). I suppose eventually my troubleshooting will involve moving the game to the now larger primary drive and disabling/dismantling the SCSI controller and unplugging the drive.

Any other ideas?

Didn't you see my post a few days ago about Cyrix 486DLC and DMA SCSI controllers? It's a serious problem getting these two things to cooperate.

Can you provide pictures of your motherboard and SCSI controller?

Here are the pics from earlier this year:

http://imgur.com/a/npm24

Ignore the first three pics (extra motherboards) The card is an AHA 1542.

Which motherboard are you using though?

Also, is your DLC cache enabled or disabled in the BIOS?

My mobo is exactly this one:

http://www.ebay.com/itm/386-Motherboard-PCCHI … 7-/201405280725

OK so I put the game on the IDE 850Mb drive, disabling the SCSI completely (removing card and unplugging the drive) Ran the game - Crash within minutes

I took out the CPU and put in the AM386DX (bloody SIDEWAYS the computer didn't even power up! Put it in correctly and it booted - What a resilient little chip!) Booted up, started the game - Crashed within 10 mins.

I pulled the cyrix co processor and played for almost an hour and then...

http://imgur.com/SrsdvwY

I put back the 486DLC and the 32 Mb RAM and the the SCSI drive and attempted to play Settlers II and it won't even get into the game - restarts almost immediately. What the hell is wrong with this system? Is Caldera DOS any good? I think next troubleshooting will be to put in a 170Mb MSDOS drive (and configure it using the MSDOS tools) - Does anyone have ANY ideas???

Try disabling the L2 cache in the BIOS. If that doesn't work, turn your memory timings down. If that doesn't work, try different memory. If that fails, the problem is probably either a bad IC or a damaged trace.

Oh yeah, and stay with IDE until your system stops crashing.

Personally I think you should use one of your other two motherboards. I think the PCchips one you have is likely the worst of the bunch. I think the ALi based one has the best potential.

I have trimmed down the timings, and stayed with IDE. Had this been the early 2000s I could have also swapped the IO card and video board (hell even EGA I had a monitor at the time) but yeah, the ALI won't take the 486DLC chip - It just won't - And I'm intent on keeping it as 386 as possible, meaning I would have to go back to a Am386DX40 with an I387 co pro (or maybe the 487 Cyrix will work?).

I'm wondering if the bus (once I get ahold of a VLB IO card - I have a VLB Mach32 hehe!) width and general performance of the ALI board will counteract the lack of 486DLC.

I suppose benchmarks are in order.

DLC is like 30% faster then 386DX. VLB helps but not that much. But do post your benchmarks 😀

https://th99.bl4ckb0x.de/m/C-D/35867.htm

There are one hell of a lot of jumpers for setting the CPU on this board. Did you remember to change them for the 486DLC?

JP31 and JP53 are the only different settings I can tell between 386 and DLC.

Some additional ideas.

1) Disable your L2 cache
2) Run MemTest 86+ v4.00
3) Disable L1 cache. What are you using to enable it?
4) What speed is your ISA bus running at? Ensure it is 7-9 MHz. Try the Keyboard clock of 7.1x MHz for the ISA bus. I recall one motherboard I used at the ATBCLK divisor for the ISA bus flipped, meaning that the more I divided the ATBCLK by, the faster the ISA bus was.
5) Try running the FSB at 33 MHz. This probably requires you to swap your oscillator, however some 386 boards have a PLL clock generator chip which allows you to set a jumper for the FSB.

So I started up the computer today and I got 8 fast POST codes, indicating a failing video card. I reseated it and it caused many weird cursor glitches. I put it into another ISA slot and moved the NVRAM around on the card and it works again. I suspect that the cause is the video card, but since I have no other card to test it with, I'm going to wait until I get my 486 parts from Poland and possibly buy a TSENG 1 Mb ISA card to further troubleshoot the video board. Otherwise, the VLB MACH 32 is going to do a severe burn-in test on the 486 I am about to build. There are many variables in this setup (as would be natural with any 20+ year old piece of tech), but I will try to maintain fidelity software-wise to try to duplicate the original problem. Thing is, I really like my MS BUS mouse!

I ran the Norton memory test (took a full 24 hrs) and there were no errors at all. Memory timing makes no difference, as does the lack/presence of SCSI. I also acquired a Compaq LTE/Lite 4/25 with 12 Mb RAM and so for now I will do further testing on that machine.

What a headache. I remember when spares literally littered the floor of my room in the late 90s. What a headache.

Do you use grounded outlet? I remember that some computer can cause all sorts of strange behavior when they aren't plugged into a grounded outlet.
Back when i was in computer repair a customer brought in his pc because it had all kinds of strange crashes. Testing it for hours on a testbench, no problem. Customer took pc home and withing an hour called again complaining the problem was still there. This went on for a few more times, until we finnaly found out that the outlet he was using was not grounded. He used a grounded outlet and no more strange crashes.

Check if the 486DLC is the BB revision. If it is remove the FPU particularly if it is Cyrix. There are certain Cyrix FPUs that do work well with BB revisions like this setup.

Also, I'm assuming you tried to install a heat-sink, at 40Mhz they get pretty hot.

BB DLC with appropriate math copro

My co pro is a little different, but also I removed it and the CPU and put in an AM386DX/40 for some time - Still crashed.

The only thing I haven't replaced is the mobo, IO card, and the video board. I'll troubleshoot each of those in a 486 I am building, for which I just picked up a NOS (unused!) AT case with P/S and new floppy.