Radeon HD 2600 XT is a middle-class GPU based on the 65nm variant of the second unified shader architecture, R600.
It's based on the RV630 Core and offers 120 Shader Processing Units, 8 TMUs and 4 ROPs a 128-bit memory interface of standard GDDR3. The central unit runs at 800MHz and the memory clock runs at up to 700MHz.
Its performance is quite superior to Radeon HD 2600 Pro due to being much higher clocked and featuring GDDR3 (thus allowing extra memory bandwidth). A GDDR4 version, which allows even more bandwidth, is also available and should be slightly faster.
Today's games are only playable at unattractive resolutions and using low (on some) or medium (maybe) presets and DirectX 11 games aren't supported.