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Power, Heat, And Efficiency

System Builder Marathon, June 2012: $2000 Performance PC

We knew that this month’s Ivy Bridge-based CPU and Kepler-based GPU would draw less power at idle than our former build’s Sandy Bridge-E and Cayman parts, but we were still surprised to see just how much power is saved by more efficient hardware. The new build uses less energy at full load than its predecessor, even when comparing its overclocked configuration to the former build’s baseline.

The new machine’s actual power consumption at the wall is less than 400 W, which means the power supply’s output was less than 360 W (according to its efficiency test sheet). If a possible SLI upgrade isn’t enough for your future-proofing needs, consider that you could run two of these complete platforms from just one of its 750 W-output power supplies.

Less power often means less heat, but we’re fully aware of the problems many Ivy Bridge-based samples have in transferring heat from the die to its integrated heat spreader. We were further disappointed to find that the only available GeForce GTX 680 graphics card uses an internally-venting cooler, increasing the temperature of the ambient air responsible for cooling the -3770K. Thus, we weren’t surprised to see a mere 1.25 V core setting push its full-load temperature to 56.4° Celsius above room temperature.

These temperature readings were taken with eight threads of Prime95 (small FFTs) running simultaneously with 3DMark 11’s first test looping, for around 30 minutes, representing a worst-case scenario.

Average performance is used to calculate both our performance-value and efficiency scores, and since this page centers on power consumption, we begin with efficiency. Overall performance is calculated using 30% games, 30% encoding, 30% productivity, and 10% storage scores.

Using our previous machine’s baseline configuration as the base for our calculations, we begin by making a direct percentage performance score for each machine. We then make an inverse power percentage calculation by dividing the baseline by each system’s actual power consumption, to award the highest power score to the machine that consumes the least energy.

The higher productivity and drive performance scores put last quarter's overclocked build on top of our performance charts. However, far lower power consumption gives the new system a huge efficiency advantage.

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