GeForce 8800 Roundup: The Best of the Best

Overclocking

As always, we looked at overclocking these already fast 8800s to see how much more we could get out of the GPU. Since none of these cards were clocked higher than reference speeds, and we covered performance of the reference 8800 GTX and 8800 GTS in the launch article, we will be focusing on overclocking, power, heat, and noise levels for this review.

We overclocked these cards by using NVIDIA's coolbits driver tweak allow us to raise the core and memory clock speeds in set increments until they reach the highest point possible while still running stable. By running stable, we mean that the cards run our benchmarks for extended periods of time without any graphical artifacts or crashes. Below is a table of the cards and the clock speeds we achieved when doing our own user overclocking on them.

Keep in mind that the factory speeds of these cards were all reference speeds; that is 575/900 for the 8800 GTX and 500/800 for the 8800 GTS. With that in mind we can see that several of these cards got fairly high overclocks, especially on the memory clock. Something we noticed when overclocking (that we will see illustrated in our overclocking performance graphs) is that like previous generations of NVIDIA cards, the core clock generally makes a more significant impact on the overall performance of the card.

Note that the current version of the driver only allows adjustment of the core and memory clocks, not the shader clock of G80. We aren't sure if the shader and core clocks are derived from the same source clock so that overclocking one actually changes the other, but we plan on looking at shader core overclocking as soon as there is software support for it. Currently there is a way to increase shader clock through a BIOS flash of the cards, but we chose to focus on overclocking that was possible without resorting to flashing your card's BIOS for this article.

The MSI GeForce 8800 GTX managed to achieve one of the highest overclocks, with the EVGA e-GeForce 8800 GTX beating it slightly on the core but not on the memory clock. The XFX 8800 GTS was able to achieve a core clock speed of higher than some of the 8800 GTXs, which is interesting, but because of its scaled down shader core it will not be able to outperform a GTX. Interestingly, the card we had higher hopes for didn't seem to overclock as well as we would have thought. The Sparkle Calibre 8800 GTX, with it's elaborate HSF design and peltier cooler, didn't get a very high memory clock at all, but did get a core boost of 56MHz on the core clock which will help performance a little.

As a final comment on overclocking, remember that your own results may vary. Given the brand-spanking-new nature of the GPU core, it could be that NVIDIA chose 575 MHz as the final core clock in order to get the most cores running at that speed. Since they aren't offering a range of GPU speeds (i.e. like CPU releases), cores either work or don't work at 575 MHz. Whether the overclocks we reached are due to variability in cores or come from actual BIOS/card differences (not that most of the cards are really different) is impossible to say without a much larger sampling of units from each manufacturer.