The final RAM specs...
"PCPer did a teardown. Great stuff... they actually read off the RAM chip (SMRT!). There's only 4 chips.
Samsung K4W4G1646B -> DDR3 4Gbit, 1.5V, 800/933/1066 speed bins -> I'm pretty sure that means "DDR3-1600/1866/2133" data rate.
256Mx16 would imply 16-bit I/O per DRAM... So... 17GB/s at most for main memory bandwidth. They didn't mention the rest of the numbers on the DRAM, but they ought to have high res photos later."
http://forum.beyond3d.com/showpost.php?p=1680114&postcount=3188
Slower than PS360 RAM... that's not seems good for AA filters and 1080p.