Reply 20 of 25, by shamino
- Rank
- l33t
The P2B boards were built with good caps, so it's unlikely to be those (even though they are old at this point).
Years ago when I used to get bulk lots of motherboards, I occasionally ran into boards that had this kind of behavior (working only when underclocked). Not sure why it happens.
A worrying thing is that it might continue to degrade until it's not stable at any usable speed. 🙁
I wonder if some aspect of the power circuitry somewhere is failing, like a dying MOSFET or something. The tests you've done don't show any obvious problem with voltages though.
One possibility (no real evidence, just a random guess) is that it could be a function of power draw from the Vcore circuit. If that were the case, then it's possible a CPU that draws less power would be able to work at a faster clock.
I'm not really advocating spending more money on random parts.. but do you happen to have a low end Coppermine? These boards frequently support Coppermine voltages but it depends what regulator chip you have. It's the ~20pin chip between the LPT port and the CPU.
Alternatively - does your P2-450MHz have a partially unlocked multiplier? Some Deschutes chips will let you set the multiplier lower, but not higher. Might be interesting to see if it can run at 100FSB with a lower multiplier like 3X or something. But I think most likely it's multiplier is locked.