I have a 486 system, usually with an s3 trio 64v+ pci. Today I tried an ati mach64 pci. It malfunctioned very intermittently - managed to boot twice out of about 10-20 attempts, but only for a few seconds. Cleaning the contacts with switch made no difference. I was thinking it was junk and I could re-use the memory chips...

Then I put it in a Celeron board. Worked fine so far, right from the start. What could explain this? Other cards seem to work in my 486 ok. Swapping them today gave a few non-boots but nothing like this ati card. Do slots get worn? Or is a short behind the board more likely?