But if you're buying a $700 graphics card, you really ought to be playing on a larger display. At the 2560-by-1600 level of our benchmarks, the Radeon HD 6990 takes advantage of that 4GB of DDR5 memory to maintain a much stronger lead -- to the tune of 35% in Dirt 2, and 64% in Far Cry 2.

Our last two games tests are even more intensive. We'll start with S.T.A.L.K.E.R.: Call of Pripyat. With an emphasis on dynamic shadows and tessellation, it's the first test that manages to pull even the lofty Radeon HD 6990 into the double digits.

A result of 30 frames per second is generally considered playable. Both the GTX 580 and the Radeon HD 6970 manage to hit that mark at the highest level of our test, but if you're playing on a 30-inch display with all of the bells and whistles cranked up, the Radeon HD 6990 remains an overall smoother experience.

The same goes for Just Cause 2, the most strenuous of our gaming tests.

In this case, the GTX 580 actually dips just under the playability line, and the Radeon HD 6970 is hanging on for dear life.