Overclocking Nehalem: The Good, The Bad And The Blue Screens

Launched in November 2008, the first three processors built on Intel's next-generation microarchitecture— formerly called Nehalem—were released under the Core i7 moniker. These CPUs, along with motherboards built around the corresponding X58 chipset, were the first products designed by Intel that take overclocking into consideration.

The high-end Core i7-965 Extreme Edition, with an unlocked clock multiplier, broke new records in performance when we reviewed it in the Test Center a few months ago. Our initial tests out of the way, we thought the time was right to see how much further the CPU could be pushed.

Originally tested on Intel's own DX58SO "Smackover" motherboard, the Core i7-965 excelled both out of the box and when slightly overclocked. But since the Smackover is somewhat limited in how many adjustments can be made, we got our hands on Asus' Rampage II Extreme, the latest in its Republic of Gamers series, which is designed specifically to overclock.

Although the Rampage II Extreme has controls on the actual board for changing settings, we stuck with the traditional way and went to work in the BIOS. The "Extreme Tweaking" tab offers an almost dizzying array of options, but we focused our attention on three in particular: the CPU ratio, the base clock frequency and the CPU's voltage.

Besides keeping an eye on the processor's speed, we also tracked how the system scored on Primate Labs' Geekbench2 benchmarking software. With the CPU at its stock speed of 3.2GHz, the system scored a more than respectable 7,998. Up to this point, that is the highest score any system has ever reached in the Test Center, bypassing the previous high of 7,429, which was achieved by a dual Xeon processor blade server.

Next we started slowly and methodically bumping up the settings, rebooting along the way. After each reboot, we let Windows load and ran Geekbench2. This was done partially to put a load on the system and confirm it was stable, but also to track the improvement in performance.

With a typical heatsink and fan cooling system, reviewers were able to run the processor at 3.87GHz. When we attempted to push it further, every reboot brought with it different signs of instability. Sometimes the machine wouldn't boot, and sometimes it would just freeze up while Windows was loading. More often than not, the system would appear OK until we tried to use it. At that point, all we saw was blue screen after blue screen.

When we finally decided we couldn't go any further, the cooling system was swapped out for a liquid cooling solution. Back in the game, reviewers were able to squeeze a little more out of the CPU.

Eventually, the blue screens started reappearing and we decided we weren't going to get any further with our current setup. Overclocked by almost 30 percent, we managed to stably bring the CPU up to 4.12GHz, close to a full GHz above its stock speed, with our final Geekbench2 score reaching 10,505.

In the near future, AMD is expected to release its 45nm Phenom II processors, while Intel has the server iteration of Nehalem following close behind. If history has taught us anything, we don't expect these latest records to stand for too long.