X1900 comes in three flavors - the XTX (MSRP $649), XT (MSRP $549), and Crossfire (MSRP $599) editions. Architecturally the X1900XTX and XT are the same; the only difference between these two cards is the speed of both core and memory. The flagship X1900XTX is clocked at 650 MHz for the core and 1.55 GHz for the memory, while the X1900XT is clocked just slightly slower at 625 MHz for the core and 1.45 GHz for the memory.