I have Inno3D GeForce 6600(NV43 REV A4) 256MB DDR2 in my rig(see signature) and I was experimenting with its overclocking abilities. I used 3D Mark 2005 Pro for testing and comparing the results.
The stock speeds are GPU:350MHz, Video RAM:700MHz.
I reached 525MHz max for the GPU, while 840MHz for the VRAM.
I did some test and concluded that both GPU&VRAM should be oced linearly in order to receive linear performance boost over the stock.
When overclocking only the VRAM from 700 to 840(120%), while the GPU remained at stock speed, there was an average of 3% boost.
But when I overclocked the GPU at 500MHz, the diference between the 840MHz VRAM VS 700MHz VRAM was 8% average boost.
When I overclocked only the GPU, while VRAM at stock speed, the performance boost was noticable, but not linear. With the GPU OCed at 525MHz (150%) I achieved about 28% overall performance boost.
With both the GPU 150% overcloked and VRAM 120% overclocked, I achieved 136% average better score on all 3D Mark 2005 Pro, tests.
I noticed that GPU OCing affected some tests, but the scores remained the same for some of the tests as nonOCed, while those tests performance was affected by OCing the VRAM.
Anyway, I need better cooling in order to play games with the GPU at 525MHz. After 30 minutes of playing F.E.A.R. invalid textures and polygons are apearing. I consider to buy new graphics card soon, so I don't want to replace the stock cooler on my GF6600. But anyway it is worth OCing the graphics card and I will do the same with the new when I buy it.