ATI R600 is Radeon X2x00 series

We can now share with you that the engineering teams at AMD created four different PCBs (Printed Circuit Boards) for the R600 GPU. These each target a different set of customers. The leaked drivers and some marketing documents already call for this generation to be called X2000 series, with devices labelled X2200 and X2400 appearing on the map.

It is not impossible that R600 just ends up being called X2800, but AMD certainly wants to have a clear branding of the product.