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Save the planet 26 November 2009 00:48
I can highly recommend using the power saving features of modern
CPU's in somebody else's computer. Well somebody have to save the
climate.
With Asus desktop motherboards the C3 and C6 states are disabled by
default. Most motherboard vendors do that. And no it won't disable
the turbo boost feature. Only the highest turbo multiplier. The i7
920 for example will still run at 2,8GHz but not 2,93GHz.
And why? Well in some respects it INCREASES performance because the
wakeup latency for the cores decreases a lot. If you use DPCLAT.EXE
to measure DPC latency for driver calls you will be scared away from
deeper C states for good. So don't do that. Save the planet instead.
Personally I even disable the C1E mode of the CPU, leaving only
speedsteep. This way I can control the throttling of the CPU in
Windows power configuration. For example 99% means "no turbo". You
can set the upper and lower bounds for CPU throttling in steps of
133MHz for the i7 (using percentages).
With AMD's CPU's even C1E mode is bad for performance since only the
very latest stepping have hardware support for it. It's disabled by
default in most BIOS's. I'm not aware that anybody actually misses
it.
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