Reaching 4GHz using nothing more than a basic air cooler was really quite easy with our QX9650 processor. It would appear that there are many other users that have had just as much success with their QX9650 processor. Once in the ASUS P5E3 Deluxe BIOS it was simply a matter of selecting the correct FSB and multiplier for the QX9650, we found that a 400MHz FSB with a 10x clock multiplier worked well. This also allowed us to work our OCZ DDR3 PC3-14400 Platinum Edition (DDR3-1800) memory at 1600MHz.

While the system would post and load Windows XP using standard voltages, stability was an issue as we were unable to complete most tests. The simple remedy was to increase the processor voltage to 1.450v and once having done so the system became 100% stable. Temperatures only slightly increased as we were now seeing a stress temperature level of just 63-66 degrees, up from 50-52 degrees at 3GHz. While just over 60 degrees might sound hot, it is in fact quite cool when compared to other high-end Intel quad-core processors that operate at these kinds of temperatures using standard voltages at their designed frequency.

Cooling the 4GHz Intel Core 2 Extreme QX9650 processor was the Thermaltake V1, which has quickly become one of our favourite heatsink and fan combos. Although we were only able to reach 4GHz with these minor BIOS tweaks, we do believe that there is even more headroom in our QX9650 processor. Through further tweaking and the use of better cooling we have little doubt that reaching a much greater operating frequency is possible. This is great news as early next year we will be presented with a whole new series of Core 2 Duo E8000 series processors based on this same 45nm design.