Here's the official stance from Abit:
<< Do the BH6 Rev. 1.00, 1.01, 1.02, 1.03, etc. and up (BUT NOT 1.1 and above) boards and the BX6 Rev 1.00, 1.01, 1.02, etc. (BUT NOT BX6 Rev 2.0) boards support Coppermine CPUs?
No, the BH6 Rev. 1.00, 1.01, 1.02, 1.03, etc. and up (BUT NOT 1.1 and above) boards and the BX6 Rev 1.00, 1.01, 1.02, etc. (BUT NOT BX6 Rev 2.0) do not support Coppermine CPUs due to the native design of power for the CPU core voltage probably not being sufficient. So to avoid instability, we advise that the afore mentioned boards do not support Coppermine CPUs. >>
The P3 FC-PGA and Celeron II FC-PGA are BOTH coppermine CPU's. Now as for Abit's stance its really a weighted chance that it will work. Abit say's not to use it to avoid instability issues. By officially saying the boards do not support the cpu they take themselves off the hook for supporting Coppermine CPU's on these boards. It is likely though that they will work since there have been a lot of people claiming success.
Since I have heard alot of people claiming success I will soon (i.e. within the next month) be attempting the P3/Celeron II usage on a BH6 1.01.
----------
Phoenix