Prior to AMD-ATI's Radeon HD 2000 series introduction, rumors circulated regarding an ultra-high clocked ATI R600-based card, that featured a large 1GB frame buffer. Some even went so far as to say the GPU would be clocked near 1GHz. When the R600 arrived in the form of the Radeon HD 2900 XT, it was outfitted with 'only' 512MB of frame buffer memory and its GPU and memory clock speeds didn't come close to the numbers in those early rumors.
Some of AMD's partners, however, have since decided to introduce R600-based products that do feature 1GB frame buffers, like the Diamond Viper HD 2900 XT 1GB in both single-card and CrossFire configurations. At 2GHz DDR, the memory on the card is also clocked higher than AMD's reference designs but the GPU remains clocked at 742MHz.