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 Yesterday, 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.