We wanted to know how far users should overclock a modern Core i7 system before the main disadvantage of overclocking—high power consumption and processor overheating—would outweigh the benefits of higher performance, by reducing the performance per watt results. What we found was not too surprising.
Hardcore Overclocking is Not Practical
The 4.0 GHz setting came out as pretty much useless for anyone who remotely cares about heat dissipation and especially power consumption. Efficiency, measured in performance per watt-hour as used in the PCMark Vantage benchmark, even decreased by 17%, while all other overclocks increased in power efficiency. The benchmark required 50% more total and also average power than the 2.66 GHz default speed. The 95% increase in peak power would still appear somewhat acceptable for enthusiasts, but the 36% increase when idle is not, as this is the minimum power the system will require at any time it is running.
Stay Reasonable for Best Results
In the case of the Core i7 920, the best setting was 3.66 GHz—at this level, the CPU delivered a massive performance boost when compared to the 2.66 GHz stock speed, while still not introducing excessive power consumption. We found that the 3.33 GHz setting makes even more sense for average users, as virtually any X58 platform for Core i7 allows the user to easily overclock the Core i7 920 from 2.66 to 3.33 GHz by increasing the system clock speed from 133 MHz to 166 MHz. You can even keep the Core i7 Turbo Mode, which accelerates an individual core by up to two multiplier increments at peak single thread load.