A few years ago Steve Jobs made a bit of a deal about the fact that the chips of the day had terrible power/watt performance. Chips then and now needed alot of power to do their calculations, they ran hot and they were inefficient, in mobile devices this combination is a battery killer. Apple wanted better and bought PA Semiconductor back in 2008 to do better.
“PA Semi is going to do system-on-chips for iPhones and iPods,” Steve Jobs
With the release of the A4 we have seen come to light Apples first home brewed System on a Chip ( SOC ). Running at 1Ghz it’s one of the fastest in the industry and being able to watch Video for 10 hours straight attests to Apple’s claims about it’s power efficiency.