Power Consumption

Cooling modern video cards is becoming more and more difficult, especially when users are asking for quiet cooling solutions. That's why the engineers are now paying much more attention to power consumption of new video card designs.

For this test we measure power consumption of only the graphics card, via PCI-Express power connector(s) and PCI-Express bus slot. A Keithley Integra 2700 with 6.5 digits is used for all measurements. Again, the values here reflect card only power consumption measured at DC VGA card inputs, not the whole system.

We chose 3DMark03 Nature as a standard test representing typical 3D usage because it offers: - very high power draw - high repeatability - is a standard benchmark that is supported by all cards - drivers are actively tested and optimized for it - supports all multi-GPU configurations - easy to obtain - fairly compact in size - test runs a constant duration and renders a non-static scene with variable complexity just like any normal game.

The four result values are as following:

• Idle: Windows 7 Aero sitting at the desktop (1280x1024 32-bit) all windows closed, drivers installed. Card left to warm up in idle until power draw is stable.
• Average: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. This results in the highest power consumption. Average of all readings (12 per second) while the test was rendering (no title screen).
• Peak: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. Highest single reading during the test.
• Maximum: Furmark Stability Test at 1280x1024, 0xAA. This results in a very high non-game power consumption that can typically be reached only with stress testing applications. Card left running stress test until power draw converged to a stable value.
• Blu-ray Playback: Power DVD 9 Ultra is used at a resolution of 1920x1200 to play back the Batman: The Dark Knight disc with GPU acceleration turned on. Playback starts around timecode 1:19 which has the highest data rates on the BD with up to 40 Mb/s. Playback left running until power draw converged to a stable value.

All across the board, in all our tests, we see massively increased power consumption of the HD 6950 1 GB vs. the 2 GB variant. This comes as a huge surprise as typically less memory at same clocks means lower power consumption. Not 35 W more! Failed, AMD.

I see several possible explanations for this. First, in idle the card does not go to 0.9 V like the 2 GB version but runs at 1.1 V, same for Blu-ray: 1.01 V vs. 1.16 V and 3D: 1.11 V vs. 1.19 V. Another reason is that the card runs a few °C hotter with 89°C which is over 10% more than the 80°C we saw on the 2 GB reference design. A silicon chip running at a higher temperature will always require more power to do the same thing. Last but not least, it is possible that the changes in the voltage regulation design resulted in another increase in power consumption.