The Diamond Viper Radeon HD 2900XT VPU core runs at 743 MHz while the 1GB of GDDR4 memory hums along at a very sweet 2 GHz! In pairs, the Diamond Viper Radeon HD 2900XT is ATI Crossfire compatible on supporting motherboards. In the review today PCSTATS overclocks the Diamond HD 2900XT 1GB's alone, and in a Crossfire pair - can you guess how fast this makes DirectX10 game playback?