<< Officially i believe its a slot one 1ghz >>
only get a slot 1 cpu for a p2b if the board is revision 1.12 or higher as those boards natively support coppermine! board revision is different to bios revision. look in between the ISA slots to check your board revision.
the limiting factor is the ability of the voltage regulator to supply the low default voltage required by the coppermine.
much safer to get a flipchip & voltage variable slocket if board revision is 1.10 or below although some 1.10 revision boards have the necessary voltage regulator to hadle a coppermine. go figger.
as for top speed, it's 1gig if you don't o/clock!