Re: On Overclocking - READ THIS!

Justin Bandholz (bandholz@vt.edu)
Tue, 06 May 1997 22:07:28 -0400


andrew meggs wrote:
> It also works with the fast clock chip in place if the
> machine is still cold and hasn't been running for more than a few hours.

...

> After isolating the problem in this amount of detail, I could reach no
> conclusion other the one I did -- that this was a timing or synchronization
> problem as a result of overclocking.

Well by your earlier statement it seems that it is not timings
that are off but the cpu temperature. Have you tried a better
heat sink and fan, possibly with some heat grease?

Most of today's cpu are well enough designed to combat clock skew
and other timing abnormalites. However, a significant change in
temperature could cause that particular functional block's
transistors to alter their bias points. This could cause a
timing problem by requiring above/below normal voltage/current
for a gate before it will trigger.

If you were having chip synchronization problems at a higher
clock frequency, you tend not to be able to boot the machine.

> If you go outside any chip's tolerances the chip
> will produce the wrong answer in some way on some calculations. > An overclocked chip will appear to work for, literally, years until it tries
> to execute that one sequence.

This is very true, the manufacturer only says it will work at a
given spec and you are on your own after that. But, typically
problems arise because of heat. Try some better cooling and see
if you can reproduce the problem.

Justin Bandholz