After posting exceptional idle system power numbers in a single-card configuration, it was surprising to find two Radeon HD 7970s using more power at idle than GeForce GTX 680s in SLI. Instead, a second Radeon HD 7970 adds about 20 W.
How about idle power use with multiple monitors attached?
|Header Cell - Column 0||Idle Power Consumption5760x1080||Display-Off Power Consumption5760x1080|
|GeForce GTX 680 2 GB||150 W||113 W|
|Radeon HD 7970 3 GB||157 W||91 W|
ZeroCore works its magic once we put our screen to sleep, though, and the CrossFire configuration immediately sheds 20 W. Not equipped with this functionality, Nvidia’s GeForce GTX 680s only manage to drop 3 W.
Dual-card configurations necessitate beefier power supplies—no doubt about that. The Radeon HD 7970s end up higher on the line graph through a run of the 3DMark 11 demo. At least in the Deep Sea segment, two GeForce GTX 680s behave an awful lot like a single GeForce GTX 590.