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AMD Cool & Quiet – how to do it right
AMD has issued a technology they call Cool & Quiet for their newer processors. The idea is to reduce their speed and core voltage when their full power is not needed, i.e. when the CPU load is low, and thus to reduce the cooling requirements significantly.
Note that these programs cannot and should not remove the cooling noise when cooling is actually needed, i.e. when you have load on the CPU.
In my tests on several computers with Athlon 64 X2 4800+ processors this technology indeed fulfilled its promise to keep them cool & quiet. However, I was tempted to rename it "Cool & Slow".
What I found was that the processor ran some 30% slower when the processor load was actually quite high. I found this utterly surprising, because it would be very simple to design the rules such that, as soon as any significant power is drawn, the processor could be made to run at full speed. I don't think that anybody would buy a 4800 processor, only to have it permanently slowed down to somewhere between 3000 and 4000.
To be fair, if you have a task that requires 100% processor load without any deterrent like disk access, then the processor is indeed run at full speed. The problem is that such tasks are exceedingly rare. A much more typical benchmark is video processing, which has high processor load plus regular disk access. That is where Cool & Quiet fails and becomes Cool & Slow.
The technology is based on a driver, which you can download from AMD's web site. This driver regulates speed and voltage, depending on processor load. However, you cannot adjust the rules. Either you install the driver or you don't.
I was asking myself how this could have come about. Were the Cool & Quiet makers stupid? But usually engineers, who invent microprocessors, aren't so stupid. What could be behind this?
The answer is fairly obvious. If you reduce the performance, you raise the demand for more.
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