[Ultima]

Quote:

but the PIII has onboard cache and there is also cache on the mobo, this can't be a problem

If that were a problem, then the problem should also occur with the P2, since it's basically the same as the P3, save a few minor changes.

well, the only thing you're changing is the cpu, so my guess would be that the bios needs an update.

And be sure that the voltage for the cpu is not too high, it's possible that the P3 runs on a lower voltage then the P2.