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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 2560x1600 resolution, using the same settings we did for performance testing.

The power consumption of the two Radeon HD 4000-series cards at idle isn't bad, but it is disappointing in light of what Nvidia has achieved with the GeForce GTX cards. The 4870, in particular, is perplexing, because GDDR5 memory is supposed to require less power. When running a game, the new Radeons look relatively better, with lower power draw than their closest competitors.

Note that those competitors include the GeForce 9800 GTX+, based on the 55nm shrink of the G92 GPU. At the same clock speeds as the 65nm XXX Edition, the GTX+-equipped system draws 11W less power at idle and 25W less under load.

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, including the stock Intel cooler we used 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 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.

I wasn't able to reliably measure noise levels for most of these systems at idle. Our test systems keep getting quieter with the addition of new power supply units and new motherboards with passive cooling and the like, as do the video cards themselves. Our test rigs at idle are too close to the sensitivity floor for our sound level meter, so I only measured noise levels under load. Even then, I wasn't able to get a good measurement for the GeForce 8800 GTX; its cooler is just too quiet.

There you have it. Not bad. However, I should warn you that we tested these noise levels on an open test bench, and the 4850 and 4870 were definitely not running their blowers at top speed. They're quite a bit louder when they first spin up, for a split second, at boot time. When crammed into the confines of your own particular case, your mileage will probably vary. In fact, for the 4850, I'd almost guarantee it, for reasons you'll see below.

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. In the case of multi-GPU configs, I only got one number out of CCC. I used the highest of the numbers from the Nvidia monitoring app. These temperatures were recorded while running the "rthdribl" demo in a window. Windowed apps only seem to use one GPU, so it's possible the dual-GPU cards could get hotter with both GPUs in action. Hard to get a temperature reading if you can't see the monitoring app, though.

The new Radeons achieve their relatively low noise levels by allowing the GPU to run at much higher temperatures than current GeForces or past Radeons. The 4850, in particular, seems to get ridiculously hot, not just in the monitoring app but on the card and cooler itself—well beyond the threshold of pain. This mofo will burn you.

I'm hopeful that board makers will find some solutions. Shortly before we went to press, we received a poorly documented and possibly incomplete set of files from Sapphire that may allow us flash to a new BIOS revision on the 4850, and I believe their aim is to reduce temperatures. I kind of worry about what they'll do to the noise levels, but perhaps we can test that. Longer term, one hopes we'll see 4850 cards with much better coolers on them, perhaps with dual slots and a rear exhaust setup, like the 4870. That would be a huge improvement.