OverclockingAs with the 7800 GTX, how the 7800 GT overclocks (beyond the factory clock) is something that we'll be looking at closely. Many of the 7800 GTXs had impressive factory overclocks, and the GT series looks to be no different. As we mentioned before, the XFX GeForce 7800 GT comes out of the box with a factory overclock of 450MHz core and 1.2GHz memory clocks. We were curious to know if we would be seeing the same core clock scaling that we saw with the GTX; specifically, if the performance increases were between the same frequencies.
Just to review, here is a brief explanation of what we saw happening with the 7800 GTX when adjusting clock speeds. Basically, we were seeing plateaus where consecutive core clock speeds had barely any impact on framerates (only a few tenths of a frame per second), then intermittent jumps up in performance between frequencies (i.e. between 472MHz and 473MHz). And because you get increasingly longer "plateaus" of minimal increase as you raise clock speeds, we've shown that this can cause for some confusion about how much faster each of the vendors' factory- overclocked 7800's really are.
After running some tests with Splinter Cell: Chaos Theory, we found that the frequencies didn't match up with what we saw with the 7800 GTX. We didn't see any jump in framerate between 472MHz/473MHz as we did with the GTX; instead, jumps occurred between 461MHz/462MHz and 477MHz/478MHz. We will be looking into this more closely in the next 7800 GT article, and hopefully, we can shed some more light on NVIDIA's frequency selection issues.
Interestingly, while attempting to overclock this card (the XFX GeForce 7800 GT), we managed to reach a core clock speed of 477MHz, which is actually a higher core speed than both the reference 7800 GTX (430MHz) and even some of the factory overclocked 7800 GTX's that we tested. This is equivalent to the performance that we would have seen at a 462MHz overclock. We did this without any special cooling systems, and the overclocking potential of these cards could be yet one more reason to choose the GT over the GTX right now. Buying a cheaper card and squeezing more performance out of it is maybe a better option than spending the extra money. But we have to say, as always, overclocking is risky and varies between cards, so if you plan on doing some overclocking yourself, we recommend paying very close attention to the warranty offered by the manufacturer.