The first two graphs above give us a look at the 7970's ZeroCore feature at work. The 7970 system's total power draw drops by 17W when the display goes into power save, almost entirely courtesy of the 7970's new low-power state for long idle. (The display's power consumption is not part of our measurement.)
Overall, the 7970's power consumption picture is quite nice. Even when idling at the Windows desktop, the newest Radeon shaves off about 5W of system-wide power consumption—more than that compared to the GeForces. When running Skyrim, the 7970 system draws a gobsmacking 80W less than the otherwise-identical GTX 580 rig. It seems the 28-nm process at TSMC is coming along quite nicely, doesn't it?
Noise levels and GPU temperatures
When ZeroCore kicks in and the 7970's fan stops spinning, we hit the noise floor for the rest of the components in our test system, mainly the PSU and the CPU cooler. By itself, without its fan spinning, the 7970 is pretty much silent.
I had hoped the bigger blower and larger exhaust venting area would make the 7970 quieter than the competition, especially since its power draw is relatively low overall. The 7970 is fairly quiet during active idle, but its fan ramps up quite a bit when running a game. Judging by the temperatures we measured, it appears AMD has biased its cooling policy toward restraining GPU temperatures rather than noise levels. I'd prefer a somewhat quieter card that runs a little hotter, personally. Still, nothing about the 7970's acoustic profile is terribly offensive; it's just not quite as nice as the GTX 580's, which is a surprise given the gap in power consumption between the two. It's a shame AMD didn't capitalize on the chance to win solidly in this category. Perhaps the various Radeon board makers can remedy the situation.