Overall Efficiency: Single- And Multi-Threaded
Overclocking from stock up to 4.7 GHz dropped the total run time of our benchmark suite by 16%.
The system needed about 30% more average system power to make this happen, though.
And here, the average energy requirement rose by about 18%
This doesn't always happen, but Intel's Core i7-3960X achieves its best efficiency right at its stock clock rate of 3.3 GHz, with Turbo Boost taking it up to 3.9 GHz in lightly-threaded workloads. Yes, there's plenty more performance to milk from Intel's flagship, but it comes at the cost of even great power use. In the end, a negative impact on efficiency draws the direction of our chart downward.
Then again, if you're spending $1050 on a processor (or even $600, if you want the Core i7-3930K), a few bucks here and there on the power bill probably isn't too big of a concern. Believe us, the point of these chips isn't lost on our enthusiast-oriented minds. But we do find it useful to know exactly what happens as a consequence of tweaking ratios and voltages in the name of more speed.