Earlier quoted context omitted.
> The power saving is not because of Android it is because of the ARM arch being used under the hood. [citation needed] Based on my understanding, the underlying OS has way more to do with power usage than the instruction set, and AFAIK Android has tons of optimizations specifically geared towards reducing battery consumption (and therefore power usage) on mobile devices. With that said, it's true that, in practice,…
It's both, if you want to achieve the goal of operating for multiple days on the battery. A modern battery powered device will have a 'sleep mode' where the current consumption is measured in microamps; and an operating mode where the current consumption is many times higher. Battery life relies on two things: Firstly, the sleep and operating modes being as efficient as possible (the CPU design) and second of all get…
My point is that this part doesn't really have much to do with the instruction set, though. Theoretically, there's no reason you couldn't design an x86 CPU that is just as efficient as an ARM one (or at least, within spitting distance); it's just not done because the economics wouldn't make sense.