Your data's not sufficient to show that. You're running two quite different workloads, and I suspect it's not clocking most of the time with the MP3 load. Now if you run the same loop with the frequency limited to 250 MHz, you'd have an accurate comparison, and I'd expect the power to scale something like V^2*F. Assuming the V^2*F WAG is right, overclocking from 600 to 850 would be the same power if you can reduce voltage from 1.35V to 1.13V, and -- assuming your workload involves doing fixed tasks followed by idling (instead of runaway loops, games that can't keep framerate up on either setting, etc.) -- the overclocked option will finish sooner and run cooler overall. So I'd guess that esthrel's comparison of 850MHz@1.2V is not harder on the CPU than stock settings for typical usage, but you're right, it is hard to say.