We measured total system power consumption at the wall socket using our fancy new Yokogawa WT210 digital power meter. 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 desktop with the Aero theme enabled. The cards were tested under load running Left 4 Dead 2 at a 1920x1080 resolution with 4X AA and 16X anisotropic filtering. We test power with Left 4 Dead 2 because we've found that the Source engine's fairly simple shaders tend to cause GPUs to draw quite a bit of power, so we think it's a solidly representative peak gaming workload.
Oh, and our graph labels have changed on this page to more fully reflect the brands of the cards being used, since custom board designs and coolers will have a major impact on power, heat, and noise. We tested only the XFX version of the 6870 here because it, the Sapphire, and the reference card from AMD all share the same cooler and board layout.
AMD led us to expect some nice reductions in idle power use with the Barts-based cards, but we just didn't see much on our power meter. Nvidia's GTX 460 cards still draw appreciably less power when they're not busy.
Barts does draw less power under load than Cypress, and Barts is also more power-efficient than the GTF104 at comparable performance levels. Those GTX 460s clocked at over 800MHz cause our test rig to pull 12W more than it does with a 6870 in the PCIe slot.
We measured noise levels on our test system, sitting on an open test bench, using an Extech model 407738 digital sound level meter. The meter was mounted on a tripod approximately 10" from the test system at a height even with the top of the video card.
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.
The differences in noise levels at idle for most of these cards aren't sufficiently large for us to say with any confidence that you'd notice them. We're simply sticking a sound level meter on a tripod next to a test system and recording a number; we don't have Steve Jobs' massive ana-whatever chamber buried six miles deep to ensure total isolation. Only the GTX 480 and better are likely to be appreciably noisier, with the one real stand-out here (in a bad way) being XFX's take on the Radeon HD 6850.
Wow, things are all over the map here, and noise levels don't seem to track with peak power consumption levels as one might expect. The Radeon HD 6850's reference cooler has hit the same basic target as the two 5800-series cards did before it, and that's not too bad. There are much quieter GeForces, though, including the Galaxy GTX 470 and EVGA's 850MHz GTX 460 FTWboth of which are very impressively quiet for their power draw levels.
Several cards are unfortunately on the noisy side, including the MSI Hawk Talon Attack, XFX's 6850, and the Radeon HD 6870's common reference cooler. I have a good sense of what's happening with the other two cards, as we'll discuss below, but the 6870's noise levels are a little disappointing for a card that draws so much less power than a Radeon HD 5870or, jeez, a GTX 480.
We used GPU-Z to log temperatures during our load testing.
Notice the presence of the two MSI cards and the XFX Radeon HD 6850 at the top of the chart above, indicating they have the lowest operating temperatures. Board makers appear to be tuning their custom coolers these days to achieve especially low temperatures, even if it means they'll be several decibels louder than necessary. When we've asked about these tuning decisions in the past, the motivations seem to be related to creating more overclocking headroom or extending the life of the GPU silicon. We can't say we like it, though, when a snazzy and obviously effective cooler like the quad-heatpipe number on the MSI Talon Attack registers two decibels above a GTX 480 on our meter. We can't help but get the sense that board makers don't share our priorities when they build in such noisy default fan speed profiles. Meanwhile, the stock cooler on EVGA's 850MHz GTX 460 is whisper quiet and keeps temperatures well within a reasonable range.
Fortunately, the folks at XFX tell me they are considering offering their users a choice by making an alternative BIOS with a quieter fan profile available on their website for this 6850. If that happens, we'll try to grab it and see how it handles.