The Inq learned a couple of things about the PlayStation 3's GPU:
It seems like the second gen dev kits were running nowhere close to full speed or spec. How close were they? Fairly.Documents shown to us on the trip showed that there were two versions, labeled 'CEB' and 'DEH'. The earlier CEB has a chip called CBE (yes, I know) connected to main memory and to a south bridge. The SB is then connected to a chip labeled 'NV4x' over a PCIe link. The upcoming version DEH has the CBE and main memory, but the NV4x/SB combo is replaced by the RSX. If you wanted to know what makes RSX more than a GPU, it looks like it is SB functionality.