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Power consumption
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 Half-Life 2 Episode Two at 1680x1050 resolution, using the same settings we did for performance testing.

One nice benefit of a low-end graphics card is low power consumption, as illustrated by these results. The Radeon HD 4670's power draw, both at idle and when running a game, is quite good, especially considering its performance. The GeForce 9600 GSO draws more power all around.

Noise levels
We measured noise levels on our test systems, sitting on an open test bench, using an Extech model 407727 digital sound level meter. The meter was mounted on a tripod approximately 12" 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.

So what happened? Quite simply, most of the cards didn't register above the ~40 dB volume threshold of our sound level meter. That's good news overall, even though it means I need to buy a new sound level meter soon. Of course, the passively cooled Zotac card isn't like to show up on any sound level meter, but the reality here is that many of these coolers, especially the custom ones on BFG Tech 9600 GT and the Palit 9800 GT, are exceptionally quiet. Some of the higher end cards are louder, especially the Radeon HD 4850 and the GeForce 9800 GTX+, because they generate more heat and must deal with it.

GPU temperatures
Per your requests, I've added GPU temperature readings to our results. I captured these using AMD's Catalyst Control Center and Nvidia's nTune Monitor, so we're basically relying on the cards to report their temperatures properly. These temperatures were recorded while running the "rthdribl" demo in a window.

You might have expected the Zotac 9500 GT with the passive cooler to run hot, but AMD's latest Radeons do, too. That seems to be the result of a conscious decision on AMD's part to tune its fan speed controllers to allow higher temperatures. The tradeoff here is that the Radeons are relatively quiet. Some folks have raised longevity concerns about video cards that run this hot, but AMD insists its cards can handle those temperatures. We're still waiting to get our hands on a Radeon HD 4850 with a custom cooler that might produce both lower temperatures and noise levels than the stock one. Again, the custom coolers from BFG and Zotac are exemplary on both fronts.

I should address a common misconception while we're talking about these things. The fact that a video card runs at higher temperatures doesn't necessarily mean it will heat up the inside of your PC more than a cooler-running card. You'll want to look at power consumption, not GPU temperatures, to get a sense of how much heat a video card produces. For example, the Radeon HD 4670 is among the hottest cards in terms of GPU temperatures, but it draws less power—and thus converts less of it into heat—than almost anything else we tested. Its higher temperatures are simply the result of the fan speed/temperature thresholds AMD has programmed into the card.