MojoKid writes "Over the last couple of weeks, the two most powerful graphics cards released for the PC to date made their respective debuts, the dual-Cayman GPU powered AMD Radeon HD 6990 and the dual-GF110 GPU powered NVIDIA GeForce GTX 590. With such powerful products in their line-ups, both AMD and NVIDIA have claimed they offer 'the world's fastest graphics card.' AMD says it's theirs. Dave Erskine, the Senior Public Relations Manager for Graphics Desktop at AMD, challenged NVIDIA directly. 'So now I issue a challenge to our competitor: prove it, don't just say it. Show us the substantiation.'"