ATI won't be using X in its Rx6xx brand names. The new Radeon generation will be branded Radeon HD 2000 series.

The R600XT or Radeon HD 2900XT is actually a 512 MB GDDR 3 card and the XTX will come later.

All the Radeon Rx6xx chips will be known as ATI Radeon HD 2000 Series.