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Maximum Efficiency: Build A 25W Performance PC Using Core i5

Test Setup And Power Consumption Results

System Hardware
Motherboard (LGA 1156)MSI H57M-ED65 (Rev. 1.0) Chipset: Intel H57, BIOS: 1.0B28 (04/01/20100)
CPU IntelIntel Core i5-661 (32nm, 3.33 GHz, 2 x 256KB L2 and 4MB L3 Cache, TDP 87W, Rev. B1)
RAM DDR3 (dual)2 x 2GB DDR3-1600 (Corsair CM3X2G1600C9DHX)
GraphicsIntel HD Graphics
Hard Drive IWestern Digital VelociRaptor, 300GB (WD3000HLFS), 10,000 RPM, SATA 3 Gb/s, 16MB Cache
Hard Drive IToshiba MK6465GSX, 640GB, 2.5," 5,400 RPM, SATA 3 Gb/s, 8MB Cache
Power Supply IPC Power & Cooling, Silencer 750EPS12V 750W
Power Supply IIFortron FSP220-60LE 220W
System Software & Drivers
Operating SystemWindows Vista Enterprise Version 6.0 x64 Service Pack 2 (Build 6000)
Drivers and Settings
Intel Chipset DriversChipset Installation Utility Ver.
Intel Storage DriversMatrix Storage Drivers Ver.

Results: Idle and Peak Power

We started off at 33W idle power, which is low but not revolutionary. We then exchanged the high-power PSU with a more efficient one.

The most important thing in this measurement is the fact that we aligned the PSU’s output to the expected system power consumption as much as possible. A 750W PSU running at only 40W load would be pretty inefficient. For this reason, the idle power decreased from 33W to only 26W. Even our small voltage decrease didn’t make much of a difference . The only other step that had an impact was the use of Toshiba’s 640GB 5,400 RPM hard drive instead of the high-performance WD VelociRaptor. Ultimately, we dropped from 33W to 23W with only two component changes. This is a 30% reduction in idle power.

Peak power doesn’t differ that much, as even the 750W Silencer power supply is operating at much more efficient levels. This is why its replacement doesn’t make as much of a difference under a heavy load. The voltage tweak, however, did make a difference of 4W. Another 2W could be saved through the more efficient hard drive.

Overall, the total impact on peak power is less significant than the change in idle power. This is where a desktop-class build will be significantly more power-hungry than a machine centering on Intel's Atom CPU. However, most desktops will spend little time using this much juice. In return, they also finish the same tasks in less time.