Overclocking
We used ATITool to automatically find the maximum core and memory clocks of our card.
In the end the card runs completely stable at 634 MHz Core (10 % overclock) and 983 MHz Memory (9 % overclock).
The 10% overclock seems to have been designed by NVIDIA that way. We have seen cards running at 1 GHz by some crazy overclockers with the right cooling.