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Power Consumption

We could have easily predicted that the new Core i7-3970X will have higher performance than its predecessor by just looking at its clock frequency. However, its higher thermal parameters make this testing a little bit more intriguing. Intel pushed the TDP back by 20 W, but we have some doubts that this is true to life. In fact, the clock frequency didn’t increase far enough to cause a 15% heat dissipation spike. Besides, the voltage intervals on the new LGA 2011 processors didn’t change a bit. In other words, we do expect some power consumption increase, but doubt that the new Core i7-3970X will consume 20 W more power under load than Core i7-3960X.

To find out more about the power consumption of all current processor models in the new AMD FX family, we performed a round of special tests. The new digital power supply unit from Corsair – AX1200i – allows monitoring consumed and produced electrical power, which we use actively during our power consumption tests. The graphs below (unless specified otherwise) show the full power draw of the computer (without the monitor) measured after the power supply. It is the total power consumption of all the system components. The PSU's efficiency is not taken into account. The CPUs are loaded by running the 64-bit version of LinX 0.6.4-AVX utility. Moreover, we enabled Turbo mode and all power-saving technologies to correctly measure computer's power draw in idle mode: C1E, C6, Enhanced Intel SpeedStep and AMD Cool’n’Quiet.

In idle mode all processors and platforms usually consume about the same power. However, in case of LGA 2011 platform this rule doesn’t quite stick. It looks like the more complex system structure including a quad-channel memory controller and a PCI Express bus controller supporting up to 40 lanes, may have affected the power consumption levels. As a result, the power appetites of systems with Core i7-3970X and Core i7-3960X in idle mode are about 20 W higher than those of simpler LGA 1155 and Socket AM3+ configurations.

Single-threaded load also shows higher power consumption levels for LGA 2011 systems. Both six-core CPUs from Intel consume even more than an eight-core AMD processor, which usually is the more power-hungry contemporary processor. However, Intel’s Sandy Bridge-E design is not cut for energy-efficiency either. Moreover, when the new processor boosts its frequency to 4.0 GHz in case of single-threaded load, it even sets the new power consumption “record” leaving its predecessor noticeably behind.

Of course, if you feel like shocking anyone with your power consumption numbers, then maximum load is the way to go. This is where Core i7-3970X is the one and only leader. Its power consumption is so high that it not only puts the system with AMD FX-8350 to shame, but also more than doubles the power readings of the LGA 1155 configuration with a Core i7-3770K. However, the power consumption difference between the system with the new Core i7-3970X and the system with the Core i7-3960X still doesn’t reach 20 W – only 12 W. In other words, the newly declared TDP have some reserves for yet another frequency boost allowing for even faster six-core Sandy Bridge-E processor to come out one day.

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