Hack 72 Overclock Your nVidia Adapter

Specifically designed for video adapters that use the nVidia chipset, nVidia's Detonator driver or the RivaTuner utility give you control over your video clock speeds.

The first thing you need to make your nVidia chipset overclockable is a small bit of Windows Registry hacking, which is made simple by downloading a file named geforce_overclock.reg within geforce_overclock.zip (link and content subject to change) from http://www.softpedia.com/public/cat/12/1/12-1-31.shtml. To merge the Registry entries in this file into the Registry:

If you want to manually apply this Registry hack (or if you can't find the download), launch regedit.exe (click StartRun and then type regedit and press Enter), navigate to (or create) the key HKEY_LOCAL_MACHINE\Software\NVIDIA Corporation\Global\NVTweak, and add a DWORD value named CoolBits and set its value to 3.

With the geforce_overclock Registry modification applied, if you already have the nVidia Detonator driver and utility software, you're all set to begin the overclocking by following these steps:

nVidia and other video card manufacturers warn that overclocking your video card's CPU or memory can damage it. While no one is specific about the damage overclocking causes, you can expect excessive heat build within the chips that can cause catastrophic failure of the components. If you overclock your video card, you should invest in and apply a larger heat sink to the video CPU and provide additional cooling across the entire card to help maintain lower overall temperatures and reliability.

Figure 7-4. Accessing the nVidia overclock settings

If your nVidia Riva-based card doesn't use the Detonator driver, set you can still ramp up your adapter with the RivaTuner utility shown in Figure 7-5, from http://www.guru3d.com/rivatuner/. RivaTuner is a simple but effective way to speed up your video.

While most of the current tweaks, Detonator drivers, and overclocking utilities indicate they are for nVidia's GeForce and Quadro products, as you see here, they work fine on the Riva and Riva TNT products dating back to 1998 also, giving new life to an older but still capable video card.

Figure 7-5. Set and save video overclock values in RivaTuner

Overclocking the CPU or "core" speed of your video card yields overall performance and frame-rate improvements proportionate to how much you increase the video card CPU speed—a 10% increase in CPU clock yields an 8-12% performance increase. In my test case, a Riva TNT-based video card running a default 90 MHz displayed an average of 12-13 frames per second (fps) before running the core clock up to 100 MHz. As mentioned earlier in this chapter, frames per second is but one measure of performance. Fps is a great benchmark for full-motion video and gaming action, but the overall quality of textures can still suffer at high frame rates, so your card needs to have high performance in rendering texture elements and smooth texture transitions. In addition, some video presentations are set at a specific frame rate, and no amount of overclocking will improve them. I experimented with an old Diamond Viper 770 card using a Riva TNT chipset and found the frame rate already maxed out at normal speed, and it did not change with higher clock speeds, but other performance measurements and the appearance of benchmarking video tests with 3DMark2001 showed calculated improvements of 8-10% and significant appearance-by-eye improvement after increasing the clock rate by 30%.