Of course, we all know that there’s a lot more to this story than price and performance. Power is a third critical consideration here.
In my initial review, The GeForce GTX 480 and Radeon HD 5870 weren’t too far apart at idle. The delta under load was quite a bit larger—but that was using FurMark.
We know for a fact (because AMD has told us) that the 5000-series cards are protected from extraneous thermal load by two features: a thermal protection mechanism that throttles clock speed beyond a set ASIC temp, and a regulator feedback signal also able to reduce clocks in response to a potentially damaging situation.
Thus, I swapped off of FurMark for this little update and went back to 3DMark’s Perlin noise test. It’s not as demanding, but it does present a fairly consistent, er, bad-case scenario. The result isn’t as extreme as the review; Nvidia’s GeForce GTX 480 uses about 64W more than the Radeon HD 5870 under load.
Adding a second card to the equation increases system power use by 337W (well over the rated board power for a single GTX 480, mind you) at load. Meanwhile, a second Radeon HD 5870 adds 162W. That's a more difficult figure to swallow (in fact, it's hard to explain, since the GTX 480 is supposed to be 250W board).