If I'm making it out right, the Elpida RAM has a -8D marking making it LPDDR2-800. That means RAM speed/bandwidth is unchanged from the Apple A5 which is disappointing considering the greater need to feed the GPU.
Could you compare the sizes of the A5 vs. the exposed A5X die? If the A5X is bigger, that would seem to indicate Apple stayed on the same Samsung 45nm process and didn't go 32nm.
Quote from Kyle Wiens:
That's what we originally thought, but it turns out there are two 1 Gb chips, for only 256 MB total. Consistent with software reports. Sorry to get your hopes up!
I guess given the software reports, there's no holding out hope that the 2Gb part number refers to each individual DRAM chip inside the A4 rather than the 2 combined?
In any case, can you confirm my interpretation of Samsung's nomenclature that the "64" in K4X2G643GE refers to a 64-bit memory bus width? If that is so, that means that regardless of RAM amount, the iPad has double the memory bandwidth of the iPhone and other smartphones which Anandtech reported to have 32-bit memory buses in their Google Nexus One review. The doubled memory bandwidth would benefit not only the CPU but also the GPU which shares system memory and bandwidth.