Power, Temperature, & Acoustics
We have a few final data points we'd like 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. We also monitored GPU core temperatures, and set up a sound level meter about six inches away from the graphics cards as well. 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.
Because the new GeForce 7800 GTX 512MB card is essentially the same as its 256MB counterpart but with much higher clock speeds, increased memory capacity, and a beefier cooler, we expected it would draw considerably more power than a 256MB GTX. It turned out that while idling at the Windows desktop, a single 512MB GeForce 7800 GTX consumed 12 more watts than a 256MB card. But in a dual-card SLI configuration, the difference dropped to only 7 watts.
Running the cards with a heavy 3D load revealed much larger differences. With two 512MB GeForce 7800 GTX cards at the heart of our test system, it consumed over 410 watts of power; 43 more watts than a pair of lower-clocked, 256MB cards. And in a single card configuration running at full load, the 512MB GeForce 7800 GTX burned though an additional 34 watts of power.
|GPU Core Temperatures|
|GF 7800 GTX 512MB||GF 7800 GTX 512MB SLI|
|Idle||49oC||50oC / 49oC|
|Load||75oC||78oC / 76oC|
We also spent some time monitoring GPU core temperatures while our test system was idling, and while it was running with a heavy 3D workload. In a single GPU configuration, the new GeForce 7800 GTX 512MB's core hovered around 49oC while idling, but with a load placed on the GPU, core temperatures shot up to about 75oC. In an SLI configuration, with two cards installed into our test system, GPU core temperatures remained largely unchanged, although they did go up by a couple of degrees depending on which GPU we monitored.
There isn't much to report with 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 graphics cards. 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 less noticeable, lower-tone, than the smaller fans found on the 256MB GTX.