Memtest86 does test the cache as well as the ram. You should clean and re-goop the heatsink as it cools the cpu core and cache. Could be just dried out goop 😁

I don't think it is a temperature issue. The CPU is of Slot 1 type. It's passively cold with giant heatsink attached to it. The problem of random restarts occurs only with certain types of operating system. The computer is solid stable with DOS and Windows 9x.

I found a CPU similar to mine on ebay and bought it. I'll test when it arrives and see if the problem is CPU-related or not (unless the other CPU is also defective! 😅)

Well what type of operating systems? Maybe you just have a BIOS setting problem.

The computer experiences random reboots with Windows NT 4.0, 2000 and recent versions of Linux distros, such as Lubuntu.

Have you done a memtest86 check as reccomended above?

My guess for the fact it doesn't crash in Dos/Win9x is that those other operating systems (NT, 2K, Linux, etc) will make extensive use of memory starting at the high end of your 512MB region; placing buffers, disk caches, etc all up there - they're all significantly more reliant on the entire region of memory working perfectly... Dos, and Win9x to a lesser extent, will all be initially running from the low end of your RAM and you may not see any issues at all due to, say, a faulty chip on a module providing ram in the region of 128-256MB.

I'd be willing to bet it's memory related - either cache or DRAM.

Are the mainboard electrolytic capacitors beyond any doubt?

@megatron-uk: I let memtest86 to run for an extended period of time and found no errors. I'll test again tonight and let it run for hours or till it completes all the tests and see.

@majestyk: I doubted the capacitors of course, but it's a pain to recap a Dolch computer! Buying a $10 replacement CPU and hoping it will fix the issue is more relaxing than thinking of disassembling the machine and recapping all boards 😅

I just tested the system again using many tools, including Memtest86, and no errors were found. I'll wait for the ordered CPU and see if that solved the problem with new OS'. If not, then I'll consider recapping the boards.

Horun wrote on 2021-04-11, 00:34:

Memtest86 does test the cache as well as the ram. You should clean and re-goop the heatsink as it cools the cpu core and cache. Could be just dried out goop 😁

Yes, I agree. It is extremely unlikely that you would pass a couple runs of memtest with bad CPU cache. I would go further than that. It is extremely unlikely that your computer would be useable at all with any kind of physical CPU damage.

If you disable L2 cache your performance drops, you use less power because you have tons of extra cache misses, and your computer is stable. I would pull apart that heatsink and replace the thermal paste and then make sure the heatsink has good thermal contact.

My board isn't stable with 256MB sticks, I would try 128MB in your place. I run with 3x128MB, it's more than enough. According to the manual I'm supposed to use 256MB only if they are registered ECC and they are right. Decreasing FSB to 66Mhz will lower CPU frequency and it could work if your problem if CPU related.

If you intend to keep PIII for a long time it may be worthwhile to get a 2nd backup board. CPUs and memory last forever, disks are plentiful but boards are not.