Power Consumption and Noise
Before we bring this article to a close, we'd like to cover a few final data points. Throughout all of our benchmarking and testing, we monitored how much power our test system was consuming using a power meter and also took some notes regarding its noise output as reported by our digital sound level meter. Our goal was to give you all an idea as to how much power each configuration used and to explain how loud the configurations were under load. Please keep in mind that we were testing total system power consumption at the outlet here, not just the power being drawn by the video cards alone.
The Radeon HD 2900 XT has an interesting power consumption profile. ATI seems to have done a good job at keeping idle power consumption relatively low. In both single and dual-card configuration, the Radeon HD 2900 XT consumed less power than any of NVIDIA's high-end solutions including the 8800 GTS. With the card running under a heavy 3D workload, however, the HD 2900 XT's power consumption skyrockets. Despite having less memory and generally fewer components on its PCB, not to mention being significantly slower, the HD 2900 XT consumes more power than a GeForce 8800 Ultra. The same holds true in the dual-card setup as well. ATI clearly won't be winning any awards in the "performance per watt" category with the 2900 XT in its current form.
We also want to talk a little bit about temperatures and noise. During our testing, we found that the Radeon HD 2900 XT - according to the data presented on the Overdrive tab - ran at temperatures between approximately 55°C and 88°C during idle / load situations. We also used an infrared thermometer to check the temperature of the PCB just behind the GPU while the card was running under load and found that went as high as 69°C. Cool running, the ATI Radeon HD 2900 XT is not.
In regard to its acoustic signature, we found the Radeon HD 2900 XT to be somewhat irritating, but not necessarily very loud. According to a digital sound level meter placed about 1 foot away from our test system (which had its side-panel removed) the Radeon HD 2900 XT generated about 55dB - 59dB of sound pressure when its fans were spun up in a typical gaming scenario. At idle, however, the cards were nice and quiet and weren't audible over the PSU and CPU fans, and hard drive. Conversely, a GeForce 8800 GTS SLI rig generated a more palatable 53dB under load.
Perhaps more noticeable than the actual sound level, however, was the pitch of the Radeon's fan. It definitely produced a much more audible whine when spinning at high-speed than the GTS, which some users may find distracting.