To overclock the Palit and XFX GeForce 9800 GTX graphics cards we ended up using Vtune, which comes with the Palit graphcis card.
The stock settings are shown above and we aimed to overclock from there using this easy software tool.
We were able to take the core from 675MHz all the way up to 800MHz and the memory from 1100MHz to 1200MHz with little effort. The most impressive part of the overclock though was the improvement on the shaders. We were able to overclock the shaders from 1688MHz to an impressive 2025MHz! This was the highest stable overclock we were able to get. We got a few benchmarks to run at 800/1250/2100, but the system would crash or lockup during testing. These are great overclocking results!
Using S.T.A.L.K.E.R. to test out the overclock we were able to notice a 15.4% performance improvement on the GeForce 9800 GTX! The GeForce 9800 GTX overclocks really good from what we have found on our two cards.