AMD is expected to launch the successor to its ATI Radeon HD 2600 in January, and now the two new parts" speed details have emerged. Graphics card maker sources cited by DigiTimes point two versions of the "RV635" GPU one an XT model, the other a Pro. The former will be clocked at 800MHz, the latter at 600MHz. The chips support DirectX 10.1 - due to be released with Windows Vista Service Pack 1 early next year. Both GPUs will connect to memory across a 128-bit bus, but while the Pro will appear on cards containing at least 512MB of GDDR 2 SDRam, XT-based cards will have 256MB of GDDR 3. As yet, memory clock speeds are not known.