Since the different versions of these cards have different coolers and clock speeds, we've tested power consumption, noise, and temperatures for both reference designs and the branded cards, as labeled below. We've also included the overclocked 7950 in the mix.
Uniquely, the Tahiti GPU is able to turn off power to most of the chip when the system has sat idle long enough for the display to go into power-saving mode. The fans on the cooler stop spinning, and the GPU requires almost no power.
The stock 7950 draws less power while running Skyrim than any other card we tested, and even the overclocked (and overvolted) XFX 7950 is relatively tame, requiring less power than a Radeon HD 6970. Note that the GeForce GTX 580-based system requires over 100W more power at the wall socket than a 7950-based system, even though the 7950-based config is faster overall.
Noise levels and GPU temperatures
Since the 7900-series cards turn off their fans when the display is off, they fare very well here. I believe some of the variance among the 7900-series cards on the dB meter comes from some electrical chatter coming from the PSU on our test system. I think it's time to replace it something a little newer, perhaps.
The most impressive combination of peak noise levels and GPU temperatures has got to be the XFX Radeon HD 7970 Black Edition's. That card, with its dual-fan cooler, is among the quietest we've tested, and the corresponding GPU temperature is only 72° C. Strangely enough, the XFX 7950 is a little bit louder despite running just one degree cooler. Regardless, both cards perform well here, as does AMD's reference-design 7950 card. We only wish the reference 7970 were a little quieter.