June 2017
Intermediate to advanced
478 pages
13h 14m
English
Running for a kilometer takes more energy than walking. In a similar way, maybe running the CPU at a lower frequency can save energy. Let's see.
The power consumption of a CPU when executing code is the sum of a static component, caused by gate leakage current, among other things, and a dynamic component, caused by switching of the gates:
Pcpu = Pstatic + Pdyn
The dynamic power component is dependent on the total capacitance of the logic gates being switched, the clock frequency, and the square of the voltage:
Pdyn = CfV2
From this, we can see that changing the frequency by itself is not going to save any power because the same number of CPU cycles have to be completed in order to execute a given subroutine. If ...
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