Thanks for clearing it up. So to sum it - over/underclocking n770 makes little sense because frequency scaling alone does not save much. Over/underclocking N800 make better sense because of possible voltage scaling (undervolting) when the clock runs slower.

But still the CPU (i.e the ARM core) is only one piece of the puzzle and when it is not used much (like the internet radio case above or most other use cases) the savings are not substantial, correct?

Do I understand it correctly that when CPU is idle it is in some sleep state where voltage/frequency doesn't matter at all so the only savings gained by D(V)FS are when CPU is actually doing something (i.e executing code)?