I used Powerstrip to overclock the 7900GT. There are few overclocking software supporting these new cards right now and powerstrip is one of them. To get above the Clock speed limit you have access to, simply double click the icons circled in red.

Then change the % value to 199. And you have a lot more MHz at your disposal.

At 1.5v and with just air-cooling on this card, it hit 745MHz and 915MHz on the Memory, totally artifact-free!

That's almost a 300MHz and 65% overclock! Do take note at over 700MHz, increasing the memory clock speed is more beneficial for performance than increasing the core speed as the card becomes memory bandwidth limited in many situations. So if you have to choose between the 2 areas to overclock, you'll know which area to pick.

From there we took the voltage to 1.6v and climbed another 35MHz on the core and 10MHz on the memory.

Up until this point, I have not increased the Memory voltage yet. I went onto increase Memory voltage to 2.2v and GPU core voltage to 1.7v.

The card was flying at 800MHz on the core and 1063MHz on the memory!! That's about an 80% overclock, and it broke through 7,000 points in 3D Mark 06. A remarkable feat for a USD$ 330 (SGD$ 550) graphics card.

Temperature wise, you can see that my air-cooling setup keeps it cool at 40C idle and 45C load right after it comes out of 3D Mark benchmark. This is roughly similar at 1.5v to 1.7v and different core speeds. The heat the card produces is really not that much even at 1.7v, and my air-cooling setup is more than sufficient to keep the card running cool.