But enough talk – let’s get down to brass tacks. We’re going to show you how to overclock your graphics card using two examples of recent cards – not that overclocking is only possible with new GPUs. It just seemed to make more sense to focus on today’s technology rather than yesterday’s.

Choose your weapons: GeForce 9600 GT and RivaTuner

We’ll start with a card from Nvidia, a GeForce 9600 GT. This card, which we tested at its recent launch, is based on a G94 GPU, a version of the G92 used in the GeForce 8800 GT and GTS V2 512 MB launched late in 2007. The G92 was itself a version of the G80 in the original GeForce 8800s that hit the market late in 2006. In other words, this is a processor with a well-known architecture and overclocking utilities that have been available long enough for us to become familiar with. The key utility for overclocking a GeForce is RivaTuner (downloadable here), an application that’s been around for some time and that gets its name from the Riva, the first GPU Nvidia produced a few years before the GeForce series. So, RivaTuner is perfectly mature and compatible with all Nvidia GPUs, and it’s updated very regularly. It’s a must-have.

Once you’ve downloaded, installed and launched the utility, click the little arrow to the right of “Customize,” in the second drop-down list entitled "Driver Settings." Select the icon that looks like a graphics card, "System settings."

The dialog that opens more or less speaks for itself. You can see three cursors – Core Clock, Shader Clock and Memory Clock.

Their function needs no explanation. But we should stop and take a closer look at the second one, for those of you who aren’t familiar with the architecture of Nvidia graphics processors. Since the GeForce 8, Nvidia GPUs have used two different clocks. One affects only the scalar ALUs (the famous stream processors) that form the unified shader units. The other affects the rest of the GPU. By default, these two frequencies are related by a ratio of approximately 2.5 (the ALUs run faster). This value isn’t universal to GeForce 8s, however, since the frequency increases by stages, as we’ll see later on.

With RivaTuner, you can increase the Core and Shader frequencies while keeping the 2.5 relation (you can also try changing that proportion). It’s not necessarily worthwhile, but it can give you a few extra MHz, since each portion of the GPU can have different frequency limits. In practice, though, you shouldn’t expect to gain all that much.