Radeon's screen tiling approach to rendering, accelerating almost everything after rasterisation if you add more GPUs, seemingly gives you compatibility with a large amount of games and can increase image quality for little to no performance cost. Screen tiles are processed by a particular GPU (or all, when anti-aliasing is being done after fragment processing) and the outputs from all are combined for display by dedicated hardware, accelerating performance and, optionally, increasing image quality.
http://www.hexus.net/content/reviews...lld19JRD0xMjE2