Power consumption and efficiency
Our workload for this test is encoding a video with x264, based on a command ripped straight from the x264 benchmark earlier in the review. The first graph below shows system power consumption over the duration of the test.
The A8-7600T completes the encoding workload much quicker than the Richland-based APUs. It also has much higher peak power consumption during the encoding process, but there's little difference in idle power draw between the AMD offerings. Meanwhile, the Core i3-4330 has lower idle and peak power consumption than anything in the AMD camp. And it finishes encoding the video file faster than the competition, too.
Note that the 45W and 65W Kaveri configs have identical idle power consumption. The lower TDP limit cuts the system's peak power consumption by almost exactly 20W, which is what we'd expect.
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.
With a slower encoding time and higher power consumption, the A8-7600 is less energy efficient than the Core i3-4330. Depending on the configuration, it requires 60-70% more energy to complete the same encoding task.
The A8-7600 and A10-6700T are pretty closely matched on the efficiency front. The Richland chip's task energy is comparable to that of the two Kaveri configs. And, since the A8-7600 finishes the encode and returns to idle faster, it consumes less energy over the full test period.
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