The Xenos GPU is something more like a prototype R600. It has less shaders (48 vs 64), and is slower (500MHz, compared with 700 for the R600).atg wrote:The Xbox 360's graphics chip is the closest to it, as it is meant to be a cut down version of the processor on this card, much like the graphics chip in the PS3 is a cut down 7800GS.
The Xenos does have a built in eDRAM framebuffer of 10MB that the R600 doesn't though, and isn't fully SM4 compatible.
Essentially, ATi used the Xenos to perfect their unified shader architecture, and R600 is the result.
The low end/mass market/real world/not for crazy people R600 products will probably be much closer to the Xbox GPU, with the distinction of their own memory and full SM4 support.