I don't have a scope available at the moment. Are you suggesting memtest to check the RAM itself or because doing so would help surface other errors? Only ask because I've tried several different RAM sticks over the last week!

mattlacey wrote on 2026-03-06, 11:58:

The system then seemed totally good in BeOS, before I realised the CPU bus was running at 66MHz not 100.

BeOS, Win 98 and Win 2000 are all behaving well with the bus at that speed, and given I don't need raw horse power from this box (using it for dev, but not compiling a lot of code) I think I'll run it like this for now because it's driving me bananas!

This to me sounds like a CPU or chipset issue.

Have you another socket 370 CPU or motherboard you could swap this out for? Is the north or south bridge exceptionally hot?

Neither of them are particularly hot, the only thing I've found that's hot is that CPU frequency generator.

Unfortunately I don't have another 370 board or CPU knocking about, though going to keep an eye on eBay for a cheap(ish) option should one come up.

Well I got hold of another CPU (866 MHz PIII) and same issue, can only run at a 66MHz CPU bus, so definitely the board. Of course with this bus speed the CPU which wants a 133 bus is only running at 433MHz, so I'm probably better off with the original Celeron in there running at 766. Will try and source a cheapish s370 board just for the sake of completeness as much as anything!

When it was working (before your first post here), was that with the Celeron? Just trying to determine it it used to work with a better CPU and then stopped (if so, seems odd that it would die with a couple different CPUs and still work fine with another (not something I'd trust much) ... or did it always die with other than the Celeron (which would suggest some sort of config/jumper problem - assuming the board officially supports the other CPUs you've tried)

Can you tell what bus speed the Celeron is working at? Seems odd that a 733 would run at a bus of 66 (it would be "curious" if it goes at 133)... but I'm not much into these details on CPUs I don't have...

Yeah that was with the Celeron. It was fine for a a few weeks (first time using it in years) but then I had the machine on for a good 4-5 hours one day - that's what seemed to kill it off. After that day I couldn't get any OS to run, they'd all lock up shortly after boot (BeOS even before the desktop was fully initialised).

The Celeron is a 1100MHz chip, designed to run on a 100MHz bus, hence the 7xx - might have been 725 based on those numbers, must have been mistaken when I wrote 733. This PIII is supposed to run on a 133Mhz bus so the drop to 66 has a bigger effect.

Sourced a replacement motherboard (not as well specced, but hey) and the machine is now working as expected. CPUs good, RAM good and all running with a 133MHz bus now I've also got a better PIII chip (900).

So definitely something up with that board, and I definitely think it's related to the PS/2 circuitry, but I think repairing it is beyond me. Will hold on to it for now but if I do get rid I'll make sure it goes to someone with better repair skills because it'd be a shame to waste it.