At 2.25V, We managed to hit 620Mhz at 5-5-5-15 stable. Click on the screenie for SuperPi 32M, 3DM01 lobby and Sandra benchmarks.

at 2.3V, we managed to do 630Mhz, stable in SuperPi 4M but not 3DM01 Lobby.

Ramping up the voltage to 2.45V and relaxing the timings to 5-6-6-18 proves fruitful, as we were able to achieve 640Mhz stable in SuperPi 4M & Lobby.

We hit wall at 645Mhz on the Asus P5KC at 2.55V, and this is only SuperPi 1M stable.