We measured total system power consumption at the wall socket using an Extech power analyzer model 380803. The monitor was plugged into a separate outlet, so its power draw was not part of our measurement. The cards were plugged into a motherboard on an open test bench.
The idle measurements were taken at the Windows Vista desktop with the Aero theme enabled. The cards were tested under load running Left 4 Dead at 2560x1600 resolution, using the same settings we did for performance testing.
The GT200 GPU has the highest dynamic range in terms of power use we've ever seen, and the 55nm version of the GT200 continues that tradition. At idle, the GeForce GTX 285 draws less power than the Radeon HD 4850, remarkably enough. Even the dual-GPU GTX 295 consumes less power at idle than a single Radeon HD 4870 512MB.
When running a game, the story changes, as the GeForce GTX cards' power use ramps up. Still, the GTX 285 draws less power than the card it replaces, the GTX 280. Disabling that ROP partition and keeping the clock speeds down on the GTX 295 seems to have had the intended effect, too: it pulls less juice than the Radeon HD 4870 X2, by over 50W.
We measured noise levels on our test systems, sitting on an open test bench, using an Extech model 407738 digital sound level meter. The meter was mounted on a tripod approximately 8" from the test system at a height even with the top of the video card. We used the OSHA-standard weighting and speed for these measurements.
You can think of these noise level measurements much like our system power consumption tests, because the entire systems' noise levels were measured. Of course, noise levels will vary greatly in the real world along with the acoustic properties of the PC enclosure used, whether the enclosure provides adequate cooling to avoid a card's highest fan speeds, placement of the enclosure in the room, and a whole range of other variables. These results should give a reasonably good picture of comparative fan noise, though.
This is our first time out with a new and improved sound meter that has a lower sound floor and seems to give more precise measurements than the old one. As a result, we've returned to measuring noise levels at idle as well as under load.
At idle, the GTX 295 produces a little more hiss than most cards, by a noticeable amount. That's a little surprising give the low noise levels achieved by a number of cards with similar power draw at idle. When running a game, also, the GTX 295 is among the loudest cards we tested. By contrast, the GTX 285 is a pretty good acoustic citizen, very much like the GeForce GTX 280 was before it.
The loudest card of the bunch, clearly, is Sapphire's Radeon HD 4850 X2. The dual fans on its cooler tend to spin pretty quickly, especially at idle, where its noise levels are simply annoying. When we asked Sapphire about this behavior, they offered us a pair of BIOS updates (the card has two BIOSes) intended to lower fan noise levels. We flashed both BIOSes following Sapphire's instructions, rebooted, and BAM! We'd bricked the card. I mean, it's fallen, and it can't get up. No POST, nada. I was going to take Sapphire to task for not providing the updated BIOS files on its website, but I can understand why the company might not want consumers attempting to flash the card's BIOSes. Bad things.
The other config that's noisy at idle is the Radeon HD 4870 1GB in CrossFire. It's loud because the primary card in the pair, the Asus EAH4870 DK 1G, is being starved for air by the second card, and the cooler has ramped up its fan speed as a result. You can see that the Asus card alone is fairly quiet at idle, at 40.3 dB. Adding a second card to the mix creates problems, though.
The dual Asus 4850s, meanwhile, remain nice and quiet as the interior card in the pair overheats.
I used GPU-Z to log temperatures during our load testing. In the case of multi-GPU setups, I recorded temperatures on the primary card.
Nvidia seems to be pretty consistent, allowing GPU temperatures to creep into the mid-80s under load, and the new GTX 285 and 295 cards fall right in line. Both the Palit and Sapphire X2 cards keep temperatures much lower than AMD's own stock coolers do, which is nice.
The shame of it all is that those Asus coolers are reasonably quiet and very effective in a single-card configuration. Look at the single-card temperature on that 4870 1GB! However, with dual cards installed, the Asus coolers essentially fail to do their jobs. These peak temperatures near 100°C were logged just before the system locked up.
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