The stock graphics card in the new Thunderbolt-y iMacs is AMD’s Radeon HD 6970M, in 1GB or 2GB flavours. How powerful is it?
It was benchmarked a few months ago. The bottom line? At the time, it was pretty fast (for Modern Warfare 2, at 1920×1080 with 4x AA and the highest detail settings it averaged 77.4fps), but not as fast as the fastest mobile chip, Nvidia’s GeForce GTX 480M series. [Tom's Hardware, Notebook Check]