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This observation arose as I was evaluating the running time efficiency of various implementations of a prime sieve algorithm.
The surprise was finding that differences between the best algorithms was much less than the 30% speedup achieved running the same algorithm (either one) just by switching from battery use to mains use.
Given that my power settings are not set to maximise battery life, I'd assumed that this would not be such a large consideration.
Any insight into to why this difference is so large?
Is it due to a software/OS induced throttling (in which case can I turn off the throttling behaviour when in battery mode?), or does the choice of power source directly affect the electrical characteristics of the chip?
(My machine: Windows XP, Intel Core2Duo, 2GHz, 2GB RAM)
PS: I'm aware that graphics card performance depends significantly on power source, e.g. discussed here, but since my benchmarking programs are console programs with no graphics and no print statements (they run in memory till 'done'), I'm not expecting the GPU to be involved... is that right?
1Your power settings may not be set on the longer life option, but they might still have a 'max CPU % while on battery' set (I'm not sure if XP can do that, but Vista+ certainly can), so check all the advanced power options for your plan. Also, take a look at your BIOS options. – Bob – 2014-05-10T11:13:35.403