We measured total system power consumption at the wall socket using a watt meter. The monitor was plugged into a separate outlet, so its power draw was not part of our measurement. The idle measurements were taken at the Windows desktop with AMD's Cool'n'Quiet CPU clock throttling function enabled. The cards were tested under load running Half-Life 2: Lost Coast at 1600x1200 resolution with 16X anisotropic filtering and HDR lighting enabled. We turned off Cool'n'Quiet for testing under load.
All of the graphics cards named below except for the two CrossFire setups were tested for power consumption on the Asus A8N32-SLI mobo. We were forced by the driver lockout to use the ATI CrossFire reference mobo instead for the CrossFire cards, so power consumption for the CrossFire systems will vary due to the difference in motherboards. Also, please note that the Radeon X1900 XT shown here is actually the CrossFire master card, so its power consumption is probably slightly higher than a non-CrossFire X1900 XT that lacks the additional chips needed for image compositing.
I believe that our Radeon X1800 XL and XT cards are not wholly representative of the idle power consumption of retail cards, either. Our cardsincluding the GTOare early review units that lack the idle clock throttling we've observed in retail Radeon X1800 cards. Our Radeon X1900 review samples, however, do settle down to somewhat lower clock speeds at idle in order to save power and cut down on heat. Unfortunately, our AIW X1900 does not.
When running Half-Life 2: Lost Coast, the idle clock issues evaporate, and we have a very clear sense of relative system-level power draw under load. As a result, the 90nm GeForce cards really come into their own. All of them draw less power than other products in their classes, but the high-end 7900 GTX may be the most remarkable; it pulls less power than a Radeon X1800 XT or an AIW X1900, let alone the higher-end Radeon X1900s. There's a 74W chasm in system power use between the 7900 GTX and the X1900 XTX on the same motherboard. Among the mid-range cards, the 7600 GT's advantage over the X1800 GTO is 20Wnot as dramatic, particularly given the differences in memory interfaces and chip size at work here, but still noteworthy.
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