While the situation with Core i7 performance was more or less clear right from the start, the power consumption levels were a little more intriguing. The thing is that Core i7-975 XE and i7-950 CPUs use new processor stepping that may make the new solutions different from the “old” CPUs of the same family in electrical and thermal parameters. That is why we were looking forward to power consumption tests this time.
The numbers below show the total power consumption of the tested platforms (without the monitor). During our tests we used 64-bit LinX 0.5.8 utility to load the systems to the utmost extent. Moreover, to ensure that we estimate the power consumption in idle mode correctly we activated all power-saving technologies, such as C1E, Cool'n'Quiet 3.0 and Enhanced Intel SpeedStep.
The numbers obtained in idle mode indicate one thing: power-saving algorithms in Nehalem CPUs with different processor steppings work almost identically. All CPUs from this series drop their frequency to 1.6GHz in idle mode that is why we see identical power consumption readings. By the way, I would also like to point out that Core i7 processors are no energy-efficient wonders. Yes, they do perform well, but the systems based on them consume more power on average than the platforms built around any other quad-core processors. You can see it from the power consumption readings taken in burn mode:
The new processor stepping did lower Core i7 power consumption a little bit. According to the obtained results, CPUs with D0 processor stepping consume about 10W less than the CPUs with older stepping working at the same frequency. And this is very good for Core i7 that can’t boast being energy-efficient at all. However, it doesn’t change the total score and the verdict remains the same: LGA1366 platform remains one of the most “power-inefficient” solutions today. And Intel is unlikely to do anything about it any time soon. Only future CPUs manufactured with 32nm process may be able to lower power consumption of Intel processors on Nehalem microarchitecture. And they are scheduled to appear in the upper price segment only in mid 2010.