The only menu in the Asus P6T Deluxe BIOS that we needed to visit in order to reach the 4.0GHz overclock with our Core i7 965 Extreme Edition processor was the “Ai Tweaker” menu. Here we simply set the Ai Overclock Tuner setting to manual, increased the CPU ratio setting to x26, and set the base clock frequency to 154MHz. This boosted the DDR3 frequency to 1540MHz, which we left it at, while the QPI frequency was slightly overclocked to 7.4GHz.

Finally, the CPU voltage was increased to 1.40v, which we considered to be quite safe and it did not cause the processor to run overly hot. Also, because we were running the memory above specification, the DRAM voltage was increased to 1.64v, which is the highest recommended setting, going higher will likely damage the processor we have been told. All other BIOS settings were left as is, meaning just six settings were altered in order to reach this impressive overclock.

Before we hung up our boots, we cracked out the Core i7 920 to see where we would end up using the cheapest of the three Core i7 processors. Now because this processor has a locked multiplier of 20x, the only way to increase the frequency is to boost the base clock. Therefore the base clock was increased from 133MHz to 190MHz, resulting in a total clock frequency of 3.80GHz, a healthy 43% overclock. Not bad for a sub-$300 Core i7 processor, and it was all made possible by the Asus P6T Deluxe motherboard.

The Core i7 920 was overclocked using the same CPU (1.40v) and memory (1.64v) voltage settings, while the memory frequency was boosted a little higher, reaching 1710MHz. However the Core i7 platform is very flexible when it comes to memory overclocking, as the memory features its own unique multiplier which works off the base clock.

For example, with the Core i7 965 Extreme Edition overclock we used a 10x clock multiplier on the memory (154 x 10 = 1540MHz). When overclocking the base clock to 190MHz, if we were to stick with the 10x multiplier the memory would be operating at 1900MHz. Although some DDR3 memory modules are rated for this frequency, with just 1.64 volts our particular memory was not.

Therefore we reduced the memory multiplier to 9x, which resulted in a memory clock frequency of 1710MHz, a frequency which our memory could handle. Of course if you have DDR3 memory that is limited to just 1066MHz or thereabouts, and you wanted to run the base clock at 190MHz, all you would have to do is reduce the memory multiplier to 6x or less.