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Efficiency

Core i5-3570K, -3550, -3550S, And -3570T: Ivy Bridge Efficiency
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If you’ve already read my launch coverage of Intel’s Ivy Bridge architecture, then you probably also saw that I charted power consumption across all of our benchmarks, facilitating an average, a precise time measurement, and a representation of watt-hours based on the product of those two.

The only hiccup we encountered was that Intel’s older Core i7-2700K wrapped up faster than the Core i7-3770K. This was because the -2700K doesn’t support DirectX 11, and consequently skipped through 3DMark 11. Thus, I’m leaving Sandy Bridge out of this comparison altogether.

It’s typically pretty hard to read these line charts, particularly with more than 30 or 40 minutes worth of data from five different CPUs crammed in. However, the peaks are perhaps most telling. We clearly see that the 77 W Core i7-3770K spikes the highest, followed by the Core i5-3550, the Core i5-3570K and Core i5-3550S fairly close together, and finally the Core i5-3570T.

In an effort to make it easier to digest that consumption information, I averaged together the lines for each CPU. The result is surprisingly subtle.

As we’d expect, the Core i7-3770K uses the most power. The other two 77 W models follow behind closely. Interestingly, the 65 W Core i5-3550S ends up less than 1 W behind the Core i5-3570K. The most significant reduction comes from the Core i5-3570T, which drops down to 82.9 W of system power, on average.

Of course, the compromise you make when you cut power is generally a corresponding loss of performance. We see a gradual scale down from the Core i7-3770K at just under 38 minutes to the Core i5-3570T, which takes almost 47 minutes to finish our benchmark suite.

All of those results trump what we saw in my original review of the Core i7-3770K. In fact, even a Core i7-3960X mated to a GeForce GTX 680 took more than an hour and nine minutes to wrap up. So, what the heck happened? Knowing that the major difference between that platform and these is integrated graphics, that PCMark 7 is able to exploit Quick Sync, and that the results we garnered for PCMark were so much higher than anything seen before, it’s safe to assume that the most significant time-savings comes from Futuremark's synthetic metric.

We can take those average power consumption numbers and multiply them by the fraction of an hour taken to complete our in-house suite to come up with energy used in watt-hours.

What we find is that the two fastest processors—both K-series SKUs—use their superior performance to finish up workloads faster. The fact that they use slightly more power, on average, than the purported low-power parts is completely counteracted by their ability to drop back to idle sooner.

Although Core i5-3550 is the least-efficient model in our comparison, the –T and –S parts fail to impress. There’s really only one reason to buy either SKU, and I’ll get into that as we wrap up.

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