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. Out of necessity, we're using a different motherboard for the CrossFire system, but for our power and noise tests, we tested the single Radeon X1950 XTX into the same motherboard as the rest of the single-card and SLI configs. Otherwise, the system components other than the video cards were kept the same.
The idle measurements were taken at the Windows desktop with SpeedStep power management enabled. The cards were tested under load running Oblivion using the game's Ultra High Quality settings at 2560x1600 resolution with 16X anisotropic filtering. SpeedStep was disabled for the load tests.
Noise levels and cooling
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 14" from the test system at a height even with the top of the video card. The meter was aimed at the very center of the test systems' motherboards, so that no airflow from the CPU or video card coolers passed directly over the meter's microphone. 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 CPU and chipset fans. We had temperature-based fan speed controls enabled on the motherboard, just as we would in a working system. We think that's a fair method of measuring, since (to give one example) running a pair of cards in SLI may cause the motherboard's coolers to work harder. The motherboard we used for all single-card and SLI configurations was the Asus P5N32-SLI SE Deluxe, which on our open test bench required an auxiliary chipset cooler. The Asus P5W DH Deluxe motherboard we used for CrossFire testing, however, didn't require a chipset cooler. In all cases, we used a Zalman CNPS9500 LED 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 cards' 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.
We measured the coolers at idle on the Windows desktop and under load while running Oblivion at 2560x1600 with 16X aniso.
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