That's true. But what about animated videos like from a game/app ? It should make something speedier. Anyways on ARM processors, everything is linked; hence SystemOnChip. Increasing the voltage overclocks the SoC, hence the cpu overclocks, as well as the bus, and consequently the gpu aswell. But it all depends on the actual driver's behaviour ofcourse, which is usually made to work acceptably and never improved after sale (at least on mobile devices). I have yet to hear any gpu overclock without cpu overclock.