Performance Scaling with OCZ's 8800 GTX

Overclocking

NVIDIA provides software, nTune, which allows users to increase the clock speed of the memory and the GPU. This functionality used to be included in their driver but it's no significant inconvenience to have it provided as a separate download. We're still pleased with NVIDIA's support of user overclocking in general. For the 8800 series, we're still waiting on support for shader overclocking, as NVIDIA has made promises but has yet to deliver.

We were able to use nTune to find optimal core and memory clock speeds but in order to perform shader overclocking we had to rely on a tool called NiBiTor, an NVIDIA BIOS editor maintained by mvktech.net. Combined with a flash utility, we were able to download the BIOS from our video card, modify the shader clock speed, and flash it with our new settings. While we can't be sure that NVIDIA's driver doesn't alter this in any way while the card is running, if you buy a card with a higher than stock shader clock speed, this is what you'll get.

The first thing we did was find a maximum stable memory clock speed. We did this by increasing memory speed and running the fuzzy cube test within ATI Tool for about 10 minutes. Once we found the highest stable memory clock speed, we used this for all our tests in order to reduce the impact of memory on overall game performance. This also serves to reduce the number of combinations of different clock speeds we would have to test.

Maximum core and shader clock speeds were found independently and tested for stability using ATI Tool. The highest stable core clock we were able to run on our OCZ hardware is 640 MHz, while we found that 1600 MHz was about as high as we could go on the shader side. We test core clock scaling with memory fixed at 1020 MHz (2040 MHz effective data rate), and shader clock fixed at 1350 MHz (stock 8800 GTX speed). Our shader clock scaling tests are performed with the same memory speed at two different core clock speeds: 575 MHz, and 640 MHz.

To put this in perspective, here's how our OCZ overclocking compares to the other cards we've already tested.

Card	Core Overclock	Memory Overclock
ASUS GeForce EN8800 GTX	629MHz	1021MHz
BFG GeForce 8800 GTX	649MHz	973MHz
EVGA e-GeForce 8800 GTX w/ ACS3	659MHz	1013MHz
Leadtek Winfast GeForce 8800 GTX	627MHz	1033MHz
MSI GeForce NX8800 GTX	652MHz	1040MHz
OCZ GeForce 8800 GTX	640MHz	1020MHz
Sparkle Calibre 8800 GTX	631MHz	914MHz
Sparkle GeForce 8800 GTX	629MHz	1011MHz
XFX GeForce 8800 GTS	654MHz	866MHz

While OCZ doesn't have the highest showing in either core or memory clock speed department, they're position is quite high on both lists. The combination of a respectable memory and core clock speed is a good thing to hope for when buying a video card to overclock.

It is important to note here that every single card will overclock differently, even if the company has binned their parts to achieve high clock speeds. Your mileage may, of course, vary.