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 UT3 at 2560x1600 resolution, using the same settings we did for performance testing.

Note that the SLI configs were, by necessity, tested on different motherboards, as noted in our testing methods section. Also, the three- and four-way SLI systems were tested with a larger, 1200W PSU.

The GeForce 9800 GTX proves predictable again, drawing just a tad bit more power than the 8800 GTS 512. Shocking.

Notice how the 9800 GTX draws quite a bit less power, both at idle and under load, than the GeForce 8800 Ultra. That fact explains what we see with the multi-GPU configs: the G92-based options draw considerably less power than the GeForce 8800 Ultra-based ones. Oddly enough, the three- and four-way G92 SLI rigs draw almost exactly the same amount of power, both at idle and when loaded. The slightly lower core and memory clocks on the 9800 GX2, combined with the fact that only two PCIe slots are involved, may explain this result.

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.

Unfortunately—or, rather, quite fortunately—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. I decided this time around that 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.

The cooler on the 9800 GTX isn't loud by any means, but it does have a bit of a high-pitched whine to it, and that shows up in our sound level meter readings. Nvidia may be taking a bit of a step back here with its reference coolers. The ones on the GeForce 8800 series were supremely quiet, and these newer coolers aren't quite as good. That's a shame.

Clustered at the bottom of the graph are the cards that required the 1200W power supply. That puppy, pardon my French, is freaking loud. Even at idle, where the 9800 GTX three-way and GX2 four-way configs both registered over 50 dB, as did the three-way Ultra rig. Under load, we're off to the symphony. Then again, did you really expect a quad SLI rig pulling over 500W at the wall socket to be quiet? Even a relatively quiet PSU would crank up its cooling fan when feeding a 500W system.