Power Consumption Greenhouse effect is the buzzword of the year and everybody is trying to do something about it, or so they say. Raw power is out, even if it buys superior performance. Energy efficiency is in, even if there is a little bit of a performance hit that goes with it. In that respect, the transition from single cores to multicore packages or to SMP computing has been a step back, that is, away from ultra low power. However, with multicore systems and a mutlithreaded software environment, the overall energy efficiency has not necessarily suffered, for the simple reason that computation times of even complex operations has sped up dramatically. Before going in to that aspect, though, let's spend a moment on the raw power envelope defined by minimum (idle) and maximum (full load) power consumption.

Windows Idle Power Consumption

One issue we were running into here was that we had to make sure that the Nehalem had throttled back to the lowest power setting. Especially after running some benchmarks, CPU-Z often reported that at least one core was still residing at a turbo setting, which skewed the measurements. Otherwise, the idle power came out the same for the i7-920 and the i7-965, which is not surprising. What was surprising, though, was how energy efficient the Nehalem actually turned out to be. Because we did not have a true i7-940 at hand we did not include the power numbers for this particular model number.

Windows Max Power Consumption

Even under full load, the Nehalem draws a lot less power than what we originally expected. To shine an even better light on things, bear in mind that the power numbers also include the integrated memory controller which, in the case of a stand-alone NorthBridge accounts for 5-12 Watt, depending on load.