Triple Monitor Performance
There's no doubt about it: you'll need a multi-GPU configuration if you want to play Dirt 3 or most other modern games across three displays with maximum quality settings. At 5040x1050, the Radeon HD 6990 averaged 59fps while the GeForce GTX 590 was slightly slower with 56fps. Conversely, the single-GPU HD 6970 mustered a paltry 34fps.
Increasing the resolution to 5760x1200 reduced the frame rate of the dual-GPU cards to just below 50fps as the HD 6990 averaged 48fps and the GTX 590 managed 46fps. The HD 6970 dipped to 28fps.
Finally, at the extreme resolution of 7680x1600, only the HD 6990 was able to deliver some semblance of playable performance with 36fps. Interestingly, while the HD 6970 averaged 21fps, the GTX 590 delivered a worthless 4fps. We've witnessed a similar problem when testing Dirt 2 at 7680x1600.