Power Consumption

Cooling modern video cards is becoming more and more difficult, especially with users asking for quiet cooling solutions, which is 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 from making 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 only reflect 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 in a relatively short time and renders a non-static scene with variable complexity.

Power consumption results of other cards on this page are measurements of the respective reference design.

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. The Card was left running the stress test until power draw converged to a stable value. We disabled the power-limiting system on cards with power-limiting systems or configured it to the highest available setting - if possible. We also used the highest single reading from a Furmark run that was obtained by taking measurements faster than 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 was left running until power draw converged to a stable value.

With the HD 7790, AMD introduces a new dynamic clock selection algorithm. It now has finer granularity with eight different clock and voltage levels and switching that occurs many times per second—all handled independently by the driver in a little microcontroller on the GPU.

As a result, power consumption in both idle and load is significantly improved. Especially gaming power draw is impressive. Compared to other HD 7790 designs that we tested, power consumption is slightly higher, but the difference is negligible. Blu-ray playback power consumption, which has always been an issue for AMD, has barely improved and is nowhere near the low numbers we see from NVIDIA cards.