Jun 07, 2012

How could overclocking improve smartphone battery life?

While discussing mobile OSes today (android is better, not iOS is better, no android is.........) my android loving office mate threw me a curveball by arguing that it was easy to improve android battery life through overclocking. Huh? That is totally counterintuitive to me. I've overclocked many a PC in my day, and the main thing I noticed as a side effect was increased heat. Heat requires energy, and more heat requires more energy, right? Is something different in android world that makes that untrue, or was he just throwing out a bogus claim? How could overclocking possibly result in better battery life?

I had to create a profile just to answer this!

It's an idea known as "race to idle". CPU clock frequency is different from CPU load. Also, scaling the frequency takes time (depending on the governor) and can increase the power needed to complete a task vs. having the CPU always clocked high.

A high clock rate that can complete a task using a low CPU load will use less battery than a low clock that needs longer and a higher load to complete the same task.

Interesting, tests have shown that maintaining a high clock rate uses the SAME amount of battery as a low clock rate. But low clock rates take more time to complete tasks. So overclocking and raising your bottom clock rate can increase battery life in normal usage.

Race to idle.

I think he isn't being clear with his terminology.  In order to overclock an Android device, you have to root it.  It isn't really the overclocking that (potentially) benefits battery life, it is gaining root access and altering voltage based on clock speeds.  Most of the time you don't use the CPU at max clock speed, whether it is overclocked or not.  So, you can lower the voltage and see little or no adverse effect.  Well, sometimes.  I've rooted an older Android phone, and I ended up just letting an app change my voltage.  It was just too much trial and error for me, and I ran into stability problems a lot trying to find the floor, but if you were more patient than me, you could theoretically achieve near perfect voltage settings.  If you rooted a device and installed a custom kernel, the voltage settings are probably already changed.  I saw a slight gain in battery life, but nothing huge.  I was always fairly careful about maximizing battery life anyway, so that might have kept my improvement to a lower level than a lot of people.   

I suspect that your office mate simply might not understand overclocking. I've never heard of overclocking saving battery power in a mobile device. It might be best though to simply let it go. If he's a real Android partisan then he might not listen to you, regardless of how well spoken you are about the issue.

Sometimes it's better to let sleeping dogs sleep...or something like that. Heh.
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