Articles: CPU

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Power Consumption

The Devil’s Canyon processors have the same semiconductor die as any other quad-core LGA1150 product, so they are going to need more power than their predecessors just because they have higher clock rates. That’s why the specified TDP is increased by 4 watts for both new models. Let’s check this out in practice.

The graphs below (unless specified otherwise) show the full power draw of the computer (without the monitor) from the wall socket. It is the total power consumption of all system components. The PSU's efficiency is taken into account but our Seasonic Platinum SS-760XP2 is a highly efficient 80 PLUS Platinum product, so its effect on the result is very small. We enable Turbo technology and all power-saving technologies: C1E, C6 and Enhanced Intel SpeedStep.

First we test our PC configurations in idle mode.

There’s no great difference between the ordinary Haswell and the Devil’s Canyon products in idle mode because power-saving technologies lower their consumption to zero. The diagrams just show the combined power draw of the mainboard, graphics card and SSD.

Next we measure the peak power consumption when our configurations run the 64-bit version of the LinX 0.6.5 utility (based on the Linpack suite) with support for the AVX2 instruction set.

What we see is the maximum power consumption we can have in practical applications. It is somewhat alarming, however, that the gap between the Haswell and Devil’s Canyon is small when we compare the Core i5 series models and large (14 watts!) when it comes to the Core i7-4790K competing against the Core i7-4770K. Of course, the senior Devil’s Canyon model has a higher clock rate and voltage but the numbers do not agree with its specified TDP. Indeed, Intel’s modern processors may consume more power in real life than their specified TDP.

The Linpack-based LinX utility makes the processor consume much more power than at average real-life loads, so we will have a more realistic test as well. We will transcode a video clip using the 64-bit x264 codec version r2453.

Once again the Devil’s Canyon products need more power than their predecessors but the numbers are not as alarming as in the previous test. Moreover, the power consumption of the new CPUs doesn't grow up as much as their performance in resource-consuming applications. It means the Core i7-4790K and Core i5-4690K have a better performance-per-watt ratio than the Core i7-4770K and Core i5-4670K, respectively.

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