This is a bit surprising as some earlier reports said it would be Radeon X2800.
Among other things we can confirm right now; R600 is 80nm, contains 700M transistors and has 512-bit memory interface. X2900 requires 2 supplemental power connector from the PSU, one 8-pin and one 6-pin but you are able to plug in the 6-pin power cable into the 8-pin connector. The targeted driver release version for X2900 series is Catalyst 8.35.1. Systems with X2900XTX cards and tech demos will be at CeBIT but inside a private room for the privileged only.