Now that we know how the new Radeons perform, let's see how the 28-nm Cape Verde GPU stacks up against the competition in terms of power efficiency. Power consumption influences GPU temperatures and noise levels, too, which we'll also be looking at.
Like Tahiti, Cape Verde gates off voltage to most of the GPU when the display goes to sleep. AMD calls that feature ZeroCore, and you can see its effects here. Idle power consumption for the whole system drops by exactly 10W when the display shuts off. (According to AMD, the 7770 and 7750 both draw around 3W of power in ZeroCore sleep mode.)
The new Radeons are also the most power-efficient of the bunch under load. Even XFX's Radeon HD 7770 Black Edition sips power despite its high core and memory speeds, which are well above reference.
If saving polar bears is your game, Cape Verde is the GPU for you.
Noise levels and GPU temperatures
With the exception of the GeForce GTX 460 (and the Radeon HD 6850 under load), none of these cards are terribly loud. The Radeon HD 7750 does have an annoying hiss to it, though, no doubt because of its small fan and single-slot heatsink. I would hope most of AMD's card partners choose either beefier active coolers or passive heatsinks.
In any case, I believe we've located the Radeon HD 7770's only tangible advantage over the cheaper 6850 right now: its quiet cooler. AMD did a good job tuning the stock cooler for low noise, which probably wasn't too hard considering the card's spartan power consumption. You might find 6850 cards on the market with less noisy coolers than our sample, but that's not a guarantee by any means.
The 7770 runs cool and quiet with the stock heatsink and fan. Nice. The 7750 isn't doing terribly well with that tiny single-slot cooler, though. We tested on an open test bench, but I wouldn't want to stick this card in a cramped enclosure with the adjacent expansion slot occupied. And I can just see that tiny, whiny little fan failing after six months.
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