@soft electrons

It very much depends on use case & how well the power is managed. If you double the clock & run for half the time then yes energy used is same or greater (depending on voltage) but, with good power managment, if you run fast there is more opportunity to sleep longer & deeper.

@soft electrons

"mobile don't care "

They will. These were lessons learned on PXA. In many cases higher clock speed = faster to sleep = lower energy.