I've got a 4750 with the 3000+ processor, and the default voltages for it were:
9X 1800Mhz 1.5V
8X 1600Mhz 1.5V
4X 800Mhz 1.1V
I conservatively dropped them to:
9X 1800Mhz 1.325V
6.5X 1300Mhz 1.15V
4X 800Mhz ...
2/12/05 at 3:19am