OverclockingTo find the maximum overclock of our card we used a combination of Rivatuner, ATITool and our benchmarking suite. Overclocking the memory was extremely easy, basically you set the clock to 1000 MHz which should always work since 1.0 ns chips are installed and then work your way up from there. When overclocking the core, the first thing you should enable is independent shader clock adjustments, then find the maximum stable shader clock. When overclocking the GPU core frequency, everything is fine until you reach about 680 MHz. From then on the overclocks revert instantly because NVIDIA has put a lock into their driver which limits the core clock to a maximum of 680 MHz. There is a grey zone of around 10 MHz which you can reach when playing around with 680 - 690 MHz clocks.
Update: As I am told people are not seeing this clock limit with the cards from XFX. Please let us know in the comments section if you experience this issue or not if you have a GeForce 8800 GS and overclock it.
Limiting the core clock makes sense from an NVIDIA business perspective because otherwise this card would kill all the GeForce 8800 GT and 8800 GTS sales.
The clocks above are the maximum we could reach with the driver's clock limit in place, already very impressive.
But of course we wanted to see if there's a way to get more out of the card. The trick here lies in modifying the BIOS to apply a higher core clock by default. Since the card has to run at some speed, the BIOS clock speed will always be set. Please note that at this time Nibitor does not support editing the GeForce 8800 GS BIOS, but I expect support to be added soon.
When attempting this, I suggest you verify first that 680 MHz core clock is perfectly stable on your card. Then you modify the BIOS to run at 690 MHz, flash the BIOS in DOS (there is no G92 flasher for Windows yet), boot into Windows and verify that this frequency is stable. If it is stable, increase the BIOS clocks by 10 MHz again and repeat. You can not change the clock speed in Windows because the driver will reject any core clock above 680 MHz.
The risk of overclocking the card too high and having a card which does not boot anymore is fairly low in my opinion because without 3D load the card will be cool and can easily handle a few MHz too much. For the sake of easier testing, the second screenshot just shows the highest core clock reached.
The final overclocks of our card are 700 MHz Core (27 % overclock) and 1039 MHz Memory (30 % overclock). I am quite sure that such high overclocks are the norm on most GeForce 8800 GS cards, because the card is essentially a GeForce 8800 GT with less memory and less power in the GPU (= cooler).
Personally I don't see much reason to pay more to get a pre-overclocked card. The overclocks go up to 680 MHz core only and ALL those cards will be limited by the driver's 680 MHz limit. So if you buy a card with 680 MHz out of the box, there will be no overclocking you can do.
Despite the massive overclocking, the card was running at acceptable temperatures at all times - and it was whisper quiet. The perfect combination in my opinion.
Those are some really amazing numbers, at the maximum core clock we reached the card could indeed beat the much more expensive GeForce 8800 GT!