Noise And Temperature
One of the biggest worries to address when it comes to adding a second graphics card is noise, which is of course an artifact of greater power consumption leading to increased heat dissipation.
Fortunately, at idle, two GeForce GTX 680s are still quieter than a single GeForce GTX 580. And although the inside card gets a little bit warmer, a single degree is hardly worth sweating.
Strangely, the inside Radeon HD 7970 heats up quite a bit more (though it’s worth noting that the outside card switches off completely and cools down to about 33 degrees).
We wouldn’t have expected trouble at idle; under load is where you see all of the action.
In this case, the inside GeForce GTX 680 gets up to 83 degrees pretty easily—warmer than a GeForce GTX 580 under load, but not as bad as prior-generation dual-slot boards.
Fortunately, the GeForce GTX 680’s fans don’t have to blow particularly hard to maintain those temperatures. A pair of GK104-based cards gets louder than a GeForce GTX 590, but they’re still less noisy than a single Radeon HD 7970. Two 7970s are pretty distracting.