Although the GTX 590's TDP rating is 10W lower than the 6990's, the new GeForce draws substantially more power here than the Radeon. This isn't an absolute max power situation—we're running a game, not a synthetic stress test or the like—so the results aren't necessarily surprising. The 6990 does look to be more power-efficient than the GTX 590, though, both at idle and when running Bad Company 2. In fact, the AUSUM 6990's power use is comparable to the stock GTX 590's. The WICKED config demonstrates why, perhaps, Nvidia hasn't pushed any harder on GPU frequencies. While the clock headroom is there, the power headroom is not.
Noise levels and GPU temperatures
Here's the eye-popping result of the day. Although the GTX 590 draws more power than the Radeon HD 6990 under load, it still registers as roughly 10 decibels quieter than the Radeon on our sound level meter. Subjectively, the difference is huge. The 6990 fills the room with a rough hissing sound, while the GTX 590 isn't much louder than an average high-end video card. Even when it's overclocked, the WICKED 590 is quieter than the stock 6990 by a fair amount.
One contributor to the difference is revealed in the GPU temperature results. The 6990's fan control profile is relatively aggressive about keeping GPU temperatures low, perhaps out of necessity. The GTX 590 lands in the middle of this pack, at least until it goes WICKED.