[H]ardOCP have snagged ATI's latest Radeon R420 Roadmap! Here's a snip.

First we have the names that will be attached to the VPUs that will scale across three levels of performance with the same VPU. The "X800XT" and the "X880XT" being the "same" card but with a different interface, with the latter being a PCI-Express X16 card. You will see that the PCI-Express core is labeled "R423" as it is in fact a native PCI-Express part and not the same CPU as the R420 with an adaptive bridge to allow the VPU to work on both interfaces.