Power Consumption

Power consumption is a very important parameter of a modern graphics card, so each new device we receive in our labs has to pass this test. The appetites of Nvidia’s GeForce 7900 GTX and 7900 GT were measured on a special testbed with the following configuration:

• Intel Pentium 4 560 CPU (3.60GHz, 1MB L2 cache)
• Intel Desktop Board D925XCV
• 2 x 512MB PC4300 DDR2 SDRAM
• Samsung SpinPoint SP1213C hard disk drive (Serial ATA-150, 8MB buffer)
• Microsoft Windows XP Pro SP2, DirectX 9.0c

We measured the power consumption of the cards with a digital multimeter Velleman DVM850BL (0.5% measurement accuracy). To put a Peak 3D load on the card we ran the first SM 3.0 graphics test from 3DMark06 in a loop at 1600x1200 resolution and with enabled 16x anisotropic filtering. Then we created an extremely high 2D load by launching the 2D Transparent Windows test from Futuremark PCMark05. Here are the results:

So, we’ve got a new record here! The new graphics card is more economical than the ex-leader GeForce 7800 GTX 512. The difference is 10 watts, which is an excellent result considering the higher clock rate of the GeForce 7900 GTX graphics processor. The power consumption of the new flagship GPU from Nvidia is in fact comparable to that of the GeForce 7800 GTX that has lower operating frequencies and less memory on board.

Note that the new card consumes the largest share, about 45W, from the PCI Express x16 slot and only about 36W from the external power line. The remaining 3W are consumed from the +3.3V line. For comparison, the Radeon X1900 XTX is almost the same load on the graphical slot, but it sucks in as much as 72W from the external +12V line! Thus, though an elite graphics card, the Nvidia GeForce 7900 GTX has a very modest appetite and doesn’t require a high-wattage power supply even if you are going to put two such cards into your system case. A good-quality 400-450W PSU will be quite enough.

The GeForce 7900 GT did well in the power consumption test, too. Having somewhat better parameters than the GeForce 7800 GTX, it consumes less power – the difference is over 30 watts! The 7900 GT is also more economical than the GeForce 7800 GT which has only 20 active pixel processors and a memory frequency of only 500 (1000) MHz. In fact, the GeForce 7900 GT consumes as much power as the GeForce 6600 GT that has only 8 pixel and 3 vertex processors! This graphics card could even do without any additional power at all since the PCI Express slot is capable of providing up to 75 watts to the installed device.

The load distribution is similar to what we saw with the GeForce 7800 GT. The GeForce 7900 GT consumes a mere 0.8W from the +3.3V line. The +12V load is evenly shared between the internal and external lines: 24 and 23 watts, respectively.

We guess there’s no need to talk about a minimum PSU wattage. Any high-quality power supply with stable output voltages will do. A SLI configuration with two GeForce 7900 GT is going to consume less than 100 watts of power, delivering a very high performance. This is an admirable achievement for Nvidia whose solutions have traditionally been more economical than ATI’s, at least in the top-end products sector.