Noise levels and cooling
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 14" from the test system at a height even with the top of the video card. The meter was aimed at the very center of the test systems' motherboards, so that no airflow from the CPU or video card coolers passed directly over the meter's microphone. 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, including CPU and chipset fans. We had temperature-based fan speed controls enabled on the motherboard, just as we would in a working system. We think that's a fair method of measuring, since (to give one example) running a pair of cards in SLI may cause the motherboard's coolers to work harder. The motherboard we used for all single-card and SLI configurations was the Asus P5N32-SLI SE Deluxe, which on our open test bench required an auxiliary chipset cooler. The Asus P5W DH Deluxe motherboard we used for CrossFire testing didn't require a chipset cooler, so those systems were inherently a little bit quieter. In all cases, we used a Zalman CNPS9500 LED to cool the CPU.

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 cards' 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.

We measured the coolers at idle on the Windows desktop and under load while playing back our Quake 4 nettimedemo. The cards were given plenty of opportunity to heat up while playing back the demo multiple times. Still, in some cases, the coolers did not ramp up to their very highest speeds under load. The Radeon X1800 GTO and Radeon X1900 cards, for instance, could have been louder had they needed to crank up their blowers to top speed. Fortunately, that wasn't necessary in this case, even after running a game for an extended period of time.

You'll see two sets of numbers for the GeForce 7950 GT below, one for the XFX cards with their passive cooling and another for the BFG Tech cards, which use the stock Nvidia active cooler. I measured them both for an obvious reason: they're going to produce very different results.

Let's talk about the BFG Tech results first, since those are the simplest to discuss. The variable-speed fan on the stock Nvidia cooler is nice and quiet at idle, right in line with the best of the bunch. As soon as you launch a 3D game, however, the BFG 7950 GT's cooler kicks into a higher gear, seemingly before the thing has any chance to warm up. Obviously, this is a mighty small cooler for such a big, fast GPU, so nobody's taking any chances. The end result is a card that's louder than anything else we've tested here. The second loudest card is the GeForce 7600 GT, which mates the same cooler with a much smaller GPU. The shame of it all is that Nvidia has vastly superior coolers in its stable, including the superb one on the GeForce 7900 GTX. You'd think Nvidia and BFG could have sprung for something a bit beefier for a video card that costs three hundred dollars or more.

Even though it eats a second slot, I prefer the cooler ATI put on the Radeon X1900 XT 256MB. That cooler is quieter under load and directs hot air out of the rear of the case. Even with its higher power consumption, the X1900 XT 256MB looks—err, sounds—pretty good compared to the BFG. Hard to believe the 7950 GT is this loud and yet draws 60W less power than the X1900 XT 256MB.

The folks at XFX must have been thinking along these lines when they decided to opt for passive cooling on their rendition of the 7950 GT. As you might have guessed, the cards are silent while running a game. Why does the actively cooled GeForce 7900 GTX produce noise meter readings in the same league? Probably because its whisper-quiet cooler moves air around the area of system and also keeps the cards themselves cooler. Like many passively cooled solutions, this XFX card tends to run quite hot, and that may be causing the system's chipset cooling fan to work a bit harder.

The XFX card's sound level readings come with a great, big caveat, though. Passive solutions like this one depend on air circulating inside of a PC case in order to work effectively. They are not really and truly passive coolers, able to radiate all of the necessary heat into the environment without the aid of a fan. We experienced this reality first-hand when the second of our XFX cards in an SLI setup on our open-air test bench began hitting the 130°C temperature threshold in the Nvidia drivers and slowing itself down. This card was positioned away from the CPU cooler and out of the path of any airflow from a cooling fan on another system component, and that proved to be a problem.

Being the self-sacrificing kind of guy I am, I decided to slap this pair of XFX 7950 GTs into my own PC for some real-world temperature testing while gaming.

The things I do for you guys. It's incredible.

Somehow I suffered through an extended session of Quake 4, after which I popped out to the desktop and found GPU temps of 89°C for GPU 1 and 85°C for GPU 2—much better than on the open-air test bench. I also did some additional testing by running a graphics demo in a window on the desktop as I worked one morning. The demo didn't take advantage of SLI, so only one GPU was active, but its temperature climbed slowly to as high as 102°C before reaching an apparent equilibrium and staying within the 100-102°C range. As Paris Hilton would say, that's hot. Whether or not that temperature is cause for concern, well, I'm not sure. Passive solutions tend to run at high temps. XFX does warrant this card for its lifetime, into its second owner, so I suppose they are confident in their product. Personally, I'm going to have to do some more game testing in SLI mode before I know for sure what to think.

Lots more, no doubt. Gotta finish Quake 4.

The moral of the story here is that passive solutions like this one are not inherently silent. They simply transfer the burden of moving air around elsewhere. In the hands of a smart system builder or inside of a good PC enclosure, that can be a very good thing indeed. Large, low-RPM case fans can be very effective while remaining nearly silent. When stuffed inside of your average PC case, though, the passive XFX card won't necessarily lead to a significantly quieter system overall.

Overclocking
Given the overheating problems we had with the XFX cards on our open-air test bench, I decided to test the overclocking potential of the GeForce 7950 GT using the BFG Tech cards instead. I also thought it would be interesting to see how well the Radeon X1900 XT 256MB could overclock, too. In both cases, I used the built-in auto-overclocking feature in the GPU maker's drivers to determine how high I could take things.

The BFG 7950 GT topped out at 598MHz GPU and 790MHz memory clocks in a single-card config, and somewhat less in SLI. The Radeon X1900 XT 256MB topped out at 698MHz GPU and 720MHz memory frequencies with a single card. The X1900 CrossFire rig wouldn't go any higher than 655MHz GPU and 720MHz memory clocks using ATI's frequency finder tool.

Overclocking puts the 7950 GT within a hair's breadth of the GeForce 7900 GTX, which isn't a bad place to be, although it doesn't mean much in terms of frames per second at this resolution. (Hey, I wanted to test something really intensive!) The X1900 XT 256MB gains some, too, from the higher clock speeds, but not in CrossFire mode, where slow memory frequencies probably hold back performance.