Power Consumption

Cooling modern video cards is becoming more and more difficult, especially when users are asking for quiet cooling solutions. That's why engineers are now paying much more attention to the power consumption of new video card designs. An optimized fan profile is also one of the few things that board vendors can do to impress with reference designs where they are prohibited to make changes to the thermal solution or components on the card.

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

We chose Crysis 2 as a standard test representing typical 3D gaming usage because it offers the following: very high power draw; high repeatability; is a current game that is supported on all cards because of its DirectX 9 roots; drivers are actively tested and optimized for it; supports all multi-GPU configurations; test runs at a relatively short time and renders a non-static scene with variable complexity.

Our results were based on the following tests:

• Idle: Windows 7 Aero sitting at the desktop (1280x1024, 32-bit) with all windows closed and drivers installed. Card left to warm up in idle mode until power draw was stable.
• Multi-monitor: Two monitors connected to the tested card, both using different display timings. Windows 7 Aero sitting at the desktop (1280x1024 32-bit) with all windows closed and drivers installed. Card left to warm up in idle mode until power draw was stable.
• Average: Crysis 2 at 1920x1200, Extreme profile, representing a typical gaming power draw. Average of all readings (12 per second) while the benchmark was rendering (no title/loading screen).
• Peak: Crysis 2 at 1920x1200, Extreme profile, representing a typical gaming power draw. 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 the stress test until power draw converged to a stable value. On cards with power-limiting systems, we disabled the power-limiting system or configured it to the highest available setting - if possible. We also used the highest single reading from a Furmark run which was obtained by measuring faster than when the power limit could kick in.
• Blu-ray Playback: Power DVD 9 Ultra was used at a resolution of 1920x1200 to play back the Batman: The Dark Knight disc with GPU acceleration turned on. Playback started 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.

Power consumption of the KFA² GTX 680 LTD OC is quite a bit higher than the NVIDIA reference design, in all power states. While it wouldn't be surprising to see increased power draw for gaming (where higher clock speeds are active), non-gaming states are increased, too. Both the GTX 680 reference design and the GTX 680 LTD OC run at 324/162 MHz, 0.99 V, in these power states, at similar temperatures, so it's most probably the radically differerent voltage regulation circuitry that makes the difference.