Our idle power measurements demonstrate the impact of AMD's ZeroCore Power feature, where the Radeon HD 7950 GPU powers down most of itself when the screen goes into power-save mode. When it kicks in, ZeroCore Power drops total system power consumption by 19W. Without it, when the system is idle at the desktop, the GTX 660 Ti draws a little less power than the 7950.
When running a game—Skyrim, in this case—the 7950-equipped system draws 20W more at the wall socket than the GTX 660 Ti-based test rig.
Noise levels and GPU temperatures
Both of these cards are reasonably quiet at idle, but the 7950 becomes virtually silent in ZeroCore Power mode, when its fans stop spinning. Then, only the faint whine of our slow-spinning CPU cooler generates any sound above the noise floor of our test environment.
Sapphire has tuned its Vapor-X cooler to maintain very low temperatures under load, likely in order to ensure lots of overclocking headroom for those who wish to tinker. They pay a price in additional fan noise, but that cooler is beefy enough to keep the noise levels fairly modest, regardless.
Personally, I prefer the fan profile Zotac has chosen for its GTX 660 Ti AMP!, which still keeps temperatures in check (67° C is practically cool, for a GPU) but holds down noise levels, as well. Even with its tiny cooler, the Zotac card makes less noise than the Sapphire.
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