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Power, Heat, And Efficiency

System Builder Marathon, Q1 2013: $1,000 Performance PC

The presence of only one graphics card gives our current build a big advantage in power consumption. It also proves that we were wrong to assume we'd need more than a 380 W power supply. Our measurements apply to the complete build, including energy lost as heat within the PSU. The 400 W maximum input reflected for our tuned configuration corresponds to a 340 W output at 85% efficiency.

Our current build’s CPU also runs much cooler at 4.40 GHz compared to last quarter's overclocked build. This is in spite of the previous build’s use of a nearly identical CPU cooler, the same core architecture, and a lower overclocked voltage. We could credit part of the current system’s relatively cool operation to our own side-fan placement optimization, but we also know that Hyper-Threading facilitates better utilization. So, doubling up on Prime95 threads could very easily tax that platform more acutely, hurting thermal performance.

Since our new system is the competitor, we used the previous build’s stock performance as the baseline for our calculations. The new build starts out 25% slower, and its overclocked configuration finishes 22% slower than Q4's tuned machine.

The purpose of calculating average performance here is that it allows us to compare average power in our efficiency chart. Those calculations result in a baseline of 100%. But we subtract 100% from all of those results, since nothing can be more than 100% efficient. The resulting chart shows how far each alternative configuration deviates from that baseline.

Lower energy consumption allows today's build, which is marginally slower, to establish big gains in energy efficiency, gaining 49.5% in stock trim and 35.6% when overclocked. The reason the overclocked configuration picks up less efficiency is because its power consumption goes up faster than performance.

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