Varying the CPU
To start with, here is the consumption of the configuration when varying the processor model or in overclocking.
As you can see, its influence is significant. The difference between the highest and lowest figures in standby in Windows desktop is 64 watts and 131 watts in load with two to four sessions of Prime95. You may have noticed that with the X6800, it’s more the rise in voltage in overclocking more than the increase in frequency that adds to power use.
Of course, in addition to the processor, Prime95 also affects these figures on the memory and chipset level. If we want to isolate the processor, we will need the ampere meter, which allows us to measure energy use of the CPU block on the mother card, whose supply varies between 80 and 90%. Here, we had a figure of 45.3 watts for the E4300 in load, versus 158.4 watts for the overclocked QX6700.
Varying the GPU
The other significant parameter in computer energy use is the graphic card. We took measurements in the Pixel Shader test in 3DMark 2006 with Prime95 in order to have a constant CPU use independent of the execution speed of 3DMark06. This choice wasn’t arbitrary, because based upon our experience, this is what offers the highest most stable use.
Even with just Windows desktop, a 8800 GTX consumes 50 watts more than a X1950 Pro. This gap increases to 92 watts in 3D. As much as this last figure is comprehensible, in 2D there is some effort to be made by manufacturers to limit a consumption that really isn’t justified. The transition to SLI noticeably increases the load and allows the deduction of the consumption of one 8800 GTX : 82 watts in 2D, 172 watts in 3D.
