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 cards were tested under load running Half-Life 2 Episode Two at 2560x1600 resolution, using the same settings we did for performance testing. At AMD's request, we've omitted power consumption results at idle because this early engineering sample doesn't yet have its power-saving PowerPlay functionality enabled, so its idle power draw isn't representative of the final products. That's unfortunate, because we're curious to see how the 4870 X2 will do at idle, especially when compared to the incredibly low idle power draw of the GeForce GTX 280.
Going with an X2 instead of two separate 4870 cards will save you a little bit on power consumption, but not much. The X2's power draw is manageable, but here's one place where going with two smaller chips instead of one larger chip may prove to be a drawback: the GeForce GTX 280 draws over 100W less power under load.
Then again, this is an early sample, and as I've said, PowerPlay isn't yet enabled. It's possible AMD may find a way to reduce power use, even under load, in the finished product.
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.
Our early 4870 X2 sample looks to be part of the trend toward relatively loud coolers in newer video cards, at least under load. Given the amount of power the card consumes and the amount of resulting heat its dual-slot cooler must dissipate, these results aren't much of a surprise. Subjectively, the X2 does seem to be pretty noisy, although to my ears, the dual GTX 280 SLI rig seemed even louder, despite what our sound level meter said.
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.
All of the Radeon HD 4800-series cards we've tested have produced some relatively high GPU temperatures, and this early X2 card is no exception. When we asked AMD about this issue in relation to the 4850 and 4870 cards now shipping, they told us the products are qualified at even higher temperatures (over 100°C) and tuned for low noise levels. In other words, these temperatures are more or less by design and not necessarily a problem.
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