We have a few final data points to cover before bringing this article to a close. Throughout all of our benchmarking, we monitored how much power our NVIDIA based test system was consuming using a power meter, and also took some notes regarding its noise output. 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 here, not just the power being drawn by the video cards alone.
There are some interesting things to note with regard to power consumption. At idle, the 7600 GT used the least amount of power, as expected considing the card's relatively small die and modest specifcation versus NVIDIA's 24-pipe parts. And under load it was clearly the least demanding card of the lot.
The GeForce 7900 GT also proved to be much more "green" than the similarly configured 256MB GeForce 7800 GTX. The 7900 GT consumed marginally less power at idle than a 256MB 7800 GTX, but under load the 7900 GT was far more energy efficient. Although clocked a bit higher than the 7800 GTX, the new 7900 GT used 41 fewer watts of power under load. NVIDIA's new GeForce 7900 GT is in a class of its own in the performance per watt category.
Thing aren't quite as rosy with the GeForce 7900 GTX, however. At idle, the GeForce 7900 GTX actually consumed more power than a 512MB GeForce 7800 GTX. We suspect the 7900 GTX's higher clock speed, in conjunction with the fact that there is likely more leakage with the 90nm G71 core, results in its high power consumption while idling. Under load though, the GeForce 7900 GTX consumed almost 20 fewer watts than the 512MB GeForce 7800 GTX.
We don't have too much to talk about in regard to each card's acoustic properties, because the sum total of noise produced by our test rig's PSU and CPU cooling fans was louder than the new GeForce cards we tested. The test system's acoustic signature, from only about 6 inches away with the side panel removed, hovered between 65db and 68db depending on which card was installed in the system at the time. We did however, get the impression that the larger fans on the 512MB GeForce 7800 GTX produced a more subdued, lower-tone, than the smaller fans found on the 7900 and 7600 GTs. When the fans on the 7600 GT and 7900 GT spun up, there was a somewhat noticable higher-pitched whine emanating from our test system, but by no means would be consider any of these new cards 'loud'.