The 9600 was still rather new when the uproar about PCI-e began. But only one 9600 version is a totally strict portover, and that's the X550 from the plain 9600. The X600 is a fairly close match to the 9600 Pro, while the X600 Pro is a slightly more distant match to the 9600 XT. The X300 is a slowed-down 9600 SE -- and the easiest way to see it clearly is putting them side by side at GPU Review. The nastiest result from all of that was the "9550", which has no relation at all to a Radeon 9500, as it is a reverse port of the X300. The foundry that ATI used for the original 9600 SE had either not been contracted with, or was running such a different new die size that the old silicon for the 9600 SE wasn't usable. In order to have a crummy enough Dx9 card in AGP to sell cheaply enough, the X300 core was used with the 9550 name.