Power, Temperatures, And Noise
Power
When most folks set up their machines, Windows 7, by default, is configured to shut off attached displays after a certain period of time and then put the entire system to sleep at some point thereafter. When we test, we don’t want those variables affecting our results, though, so we turn it all off.
Thus, the power numbers in the chart above reflect idle power consumption sitting on the Windows desktop—and they’re impressive to say the least. AMD’s single-GPU boards—current-generation and last-generation—prove themselves to be the best in this metric.
But the company went one step further with the ZeroCore feature set we introduced in AMD Radeon HD 7970: Promising Performance, Paper-Launched. The result of ZeroCore is even lower power draw once output to the display is cut.
The Radeon HD 7950 leads the way, with an idle system power consumption just over 93 W (that’s a Core i7-3960X-powered platform with 16 GB running at 4.2 GHz, remember).
If you think that’s cool, it gets better on the next page.
Clearly, AMD’s Radeon HD 6990 and Nvidia’s GeForce GTX 590 are the highest power consumers. Comparatively, the Radeon HD 7950, which averages 315 W of system power use across this test to the 6990’s 450 W and the GTX 590’s 490 W, is downright eco-friendly.
Temperature
The two 28 nm Tahiti-based GPUs run significantly cooler than the 40 nm competition at idle.
Whereas most of the cards tested in a Metro 2033 loop are cooled in a way that keeps them from exceeding 86 degrees C, the Radeon HD 7900s want to stay in the 70s—and their fans blow hard enough to make sure that happens.
Noise
From exactly one meter behind each card’s rear I/O port, idle noise is fairly similar. In fact, although we went so far as to use a closed-loop liquid cooler for its quiet operation, the unit’s built-in pump was the loudest component on our test bench.
In an effort to keep each card within preset thermal limits, these boards all employ different fan speed profiles.
The Radeon HD 6990 is notoriously obtrusive. Despite AMD’s claims that we ended up with a defective sample, we have two of these things running in the lab, and they’re both noisy beasts.
Despite lessons we would have hoped AMD's engineers would have learned from the Radeon HD 6990, though, and even though this new architecture doesn’t get particularly hot under a normal load, the Radeon HD 7970’s fan is also disturbingly loud. It’s not as outright-obscene as the dual-GPU card. However, the company’s design guys could certainly take a hint or two from the effort that went into Nvidia’s GF110-based boards. Even the power-hungry GeForce GTX 590 runs quieter than the new Radeon HD 7950 on display today.
