Please note that overclocking the AGP bus is a rather hazardous operation. Mild problems arising from overclocking the AGP bus include texture corruption, "wireframe" effects and in more serious cases, system lock-ups. These problems are not really dangerous because they will not cause permanent damage and are easily correctable by immediately reducing the speed of the AGP bus.

However, it's possible to permanently damage the AGP card while overclocking the AGP bus. While I have yet to damage any of my cards while overclocking the AGP bus so far, there have been many reports from others who have suffered permanent damage to their cards while attempting to overclock the AGP bus. When that happens, there's nothing they can do about the cards except return them for replacements, if possible or buy new ones.

So, beware when overclocking the AGP bus. To reduce the risk of permanently damaging your card, please follow the precautions :-

• provide adequate active cooling for both the AGP card and the motherboard's north bridge chip.
• overclock the AGP bus step by step - overclock from 66MHz to 75MHz first before trying out 83MHz and so on.
• test the overclocked AGP bus comprehensively using benchmarks and game demos before attempting the next speed level.
• if you encounter any problem at all after overclocking the AGP bus, immediately shut down and reduce the AGP bus speed.

These precautions may not offer you 100% protection against damage to your card but they will provide you with a real margin of safety. Now that we are all aware of the dangers of overclocking the AGP bus, let's get back to the how of AGP bus overclocking...

The AGP bus specification calls for a clockspeed of 66MHz for both AGP1X and AGP2X transfer protocols. In order to double the transfer rate over that of AGP1X, AGP2X transfers data on both the rising and falling edges of the AGP signal. It does not run at a doubled clockspeed of 133MHz, despite what many may think. So, overclocking the AGP bus involves nothing more than pushing the clockspeed beyond 66MHz. How do we go about that?