Check out the manufacturers site, it should tell you. My Abit BE6 (original) is also a BX board and can handle up to a PIII-850 (100MHz FSB) officially. If your MB can provide the lower voltage needed for a Coppermine than I would guess you could probably handle the same, otherwise I'd say a PIII-600 Katmai core (no E or B) is the fastest you can go.