Power Consumption and Acoustics
Before bringing this article to a close, we'd like to cover a few final data points--namely power consumption and noise. Throughout all of our benchmarking and testing, we monitored how much power our test system was consuming using a power meter. Our goal was to give you all an idea as to how much power each configuration used while idling and while under a heavy workload. Please keep in mind that we were testing total system power consumption at the outlet here, not just the power being drawn by the graphics cards alone.
After witnessing the Radeon HD 5870's excellent performance throughout the benchmark testing, we were impressed by its power consumption characteristics. AMD claimed significantly reduced power consumption while idle and only slightly higher power consumption than the previous generation while under load. Our tests proved out the idle-power claims, as the Radeon HD 5870 clearly used the least amount of power. And while under load, the Radeon HD 5870 also finished a bit lower than the 4890. We suspect that power consumption will differ a bit from card to card due to GPU yields using TSMC's 40nm process, but regardless of that possibility, better than Radeon HD 4870 X2 performance with power consumption that's about ~150 watts lower is a testament to the 5870's power efficiency.
While we're talking power, we should also talk noise for a bit. Although AMD claimed the bearings used in the Radeon HD 5870's fan would result in a lower-pitched noise than the 4890's, we couldn't hear much of a difference when the fans on each card spun up. However, despite its strong performance, the Radeon HD 5870's fan spun up far less than the 4890's, which resulted in a quieter experience overall. While idling the Radeon HD 5870 is, for all intents and purposes, inaudible. Under load, the card's fan is audible, but we would not consider it noisy by any means.
We should also point out that despite its complexity, the Radeon HD 5870 also runs relatively cool. While idling, we witnessed GPU temperatures in the mid-40'C range. While under load, that number shot up into the mid-80'C range.