The Retina MacBook Pro actually has two video cards—one integrated, one discrete. The integrated video card (which shares memory with the main memory, and is actually part of the CPU), is Intel’s HD Graphics 4000, which is used to help preserve battery life. The discrete video card (a separate component with its own memory) is Nvidia’s GeForce GT 650M, with 1GB of video memory. The system automatically switches processors based on the activity you’re performing, so you’re not sacrificing performance while, say, playing a game. You can turn off automatic graphics switching, which then sets the Retina MacBook Pro to always use the discrete video card.
Looks like GT 650M is a backup...smart..
Apple can tailor its iOS to do what it wants, no big deal..but for Microsoft since Windows is a more generic OS, a little bit harder though..