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Power consumption and efficiency
Since power efficiency is another one of Haswell's big highlights, we'll head there next. The workload for this test is encoding a video with x264, based on a command ripped straight from the x264 benchmark you'll see later. The first set of plots comes from our standard test systems with discrete Radeon graphics. The second set shows system-level power consumption with only the integrated graphics processors in use.

Interesting. Our 4770K-based test system offers a nice decrease in idle power draw compared to the Ivy-based 3770K, but only with integrated graphics. Once you pop in a graphics card, the reduction in power draw is only about 5W—and the 4770K system doesn't even have the lowest idle power draw of the desktop processors we've tested. That distinction goes to the AMD A10 APU.

By spec, the 4770K has a 7W higher power ceiling than the 3770K. In this test, the difference in total system power consumption boils down to just 1-2W. The AMD CPUs, meanwhile, consume quite a bit more juice.

We can quantify efficiency by looking at the amount of power used, in kilojoules, during the entirety of our test period, when the chips are busy and at idle.

Perhaps our best measure of CPU power efficiency is task energy: the amount of energy used while encoding our video. This measure rewards CPUs for finishing the job sooner, but it doesn't account for power draw at idle.

The 4770K requires the least power to complete the encoding task even though its peak power draw is slightly higher than the 3770K's. Credit for that win should go to the AVX2 and FMA extensions in the Haswell core, which are supported in the version of the x264 encoder we're using. They help the 4770K finish the encoding task sooner.

If you want a single set of numbers to summarize AMD's struggles of late, look no further than the chart above. Even though the FX-8350 also supports FMA, it requires more than twice the energy to complete the same task as the 4770K. The FX processor's absolute performance is lower and its peak power draw is substantially higher. Not a recipe for success.