I got my friend a 566 OEM last summer and that thing is a little gem. She does over a 1000 but needs more cooling then the Golden Orb he has on it so it rides at 933 for now, and at 1.70 volts. The 633 will do 100mhz at around 1.8 volts and I had one that does 997 on an Golden Orb, will do more but needs better HSF.