Power Consumption / Temperature Testing
For this section, every energy saving feature was enabled in the respective BIOSes and the Windows Vista power plan was changed from High Performance to Balanced.
For our idle test, we let the system idle for 15 minutes and measured the peak wattage through our UPM EM100 power meter.
For our CPU load test, we ran Prime 95 In-place large FFTs on all available threads for 15 minutes, measuring the peak wattage via the UPM EM100 power meter.
For our overall system load test, we ran Prime 95 In-place large FFTs on all available threads for 15 minutes, while simultaneously loading the GPU with OCCT v3.1.0 GPU:OCCT stress test at 1680x1050@60Hz in full screen mode.
Considering the performance these two CPUs put forward, their power consumption numbers are really something to behold and they speak volumes about the maturity of Intel's 32nm manufacturing process. As a comparison, the new 2500K consumes about as much as the highly popular Core 2 Duo E8400; now that's progress!
Now onto the power consumption when using the IGP instead of a power hungry discrete GPU...
Power consumption numbers with the IGP enabled are interesting to say the least. It seems like the additional on-board graphics capabilities comes with a notable decrease in overall efficiency but considering the gap between the Clarkdale and Sandy Bridge graphics cores in performance, this was to be expected.
For the temperature testing, we used both the two stock Intel Sandy Bridge CPU coolers and a Thermalright Ultra-120 Extreme (TRUE). The ambient temperature was 24°C/75°F. The application used to monitor temperatures was HWMonitor 1.17.1.
Idle CPU + Idle IGP: The system was left to idle for 15 minutes.
Idle GPU + Load IGP: OCCT v3.1.0 GPU stress test was run at 1680x1050 for 15 minutes.
Load CPU + Idle IGP: Prime 95 In-place large FFTs was run for 15 minutes.
Load CPU + Load IGP: Prime 95 In-place large FFTs and OCCT v3.1.0 GPU stress test were run for 15 minutes.
With and without an aftermarket heatsink, the new Sandy Bridge processors are some cool-running products considering the clock speeds which they operate at. The reasoning behind the 2500K's higher reference temperatures boils down to the smaller, lower quality stock heatsink it comes with.
To see just how much (or little) the IGP contributed to the overall heat output we also measures temperatures while the IGP was idling and under full load. The below temps were achieved with Thermalright Ultra-120 Extreme in order to achieve normalized numbers.
Naturally, with the graphics core enabled the temperatures do tend to increase as more of the chip's transistors are being used. The increase however is anything but dramatic.
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