while there has been lots of speculation, IGN have apparently been given a source detailing the consoles specs.
“…may utilize custom chips based on AMD’s A8-3850 APU and Radeon HD 7670 GPU, sources have told IGN, offering the combined performance of both integrated and discrete graphics processors.”
Interestingly enough, the 7670 is a rebrand of the exact same card that’s featured (or at least rumored to be featured) in the Xbox 720, (the ATI 6670).
While this doesn’t sound impressive in PC terms, the Playstation 4 will be using Asymmetrical CrossFire to share load of realtime graphics processing thanks to the oboard A8-3850.
More details on IGN