In addition to what other posters have noted... there are rumors that future AMD APUs are going to support both DDR4 and GDDR5 RAM.

http://hardware-beta.slashdot.org/story/14/01/20/0159210/amd...

AMD has had sub-par (compared to Intel) memory controllers recently. So maybe the improved memory is for naught. Nonetheless, they're working on it...