Power consumption
We measured total system power consumption at the wall socket using a watt meter. The monitor was plugged into a separate outlet, so its power draw was not part of our measurement. To keep things even, we did our power consumption testing for all cards using the Asus A8R32-MVP Deluxe motherboard.

The idle measurements were taken at the Windows desktop with AMD's Cool'n'Quiet CPU clock throttling function disabled. The cards were tested under load running Oblivion using the game's High Quality setting at 1600x1200 resolution with 16X anisotropic filtering.

Unsurprisingly, the GX2 consumes more power when sitting at the Windows desktop than any of the single-GPU cards. The shocking thing is the power use under load. The Radeon X1900 XT-based system draws 27 watts more power at the outlet than the otherwise-identical GX2-based rig. Craziness.

Ok, maybe it's not so crazy. We've seen similar achievements with dual-core CPUs, after all. And the GX2 certainly acts the part; its cooler seems a little quieter under load the Radeon X1900 XTX's. The GX2 isn't as whisper quiet as the GeForce 7900 GTX, but it's pretty darned good, considering.