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 relatively short time and renders a non-static scene with variable complexity.

Our results are 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 is 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 is 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 is obtained by measuring faster than when the power limit can 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.

In non-gaming states Gigabyte's card needs quite a bit more juice than both the normal HD 7970 and the GHz Edition. In this scenario voltages, clocks and temperature are similar or better, so the only explanation I see is the completely different voltage regulation circuitry. Another factor could be the extremely low ASIC quality rating as reported by GPU-Z. While this may sound bad at first, a low quality rating is something sought by extreme overclockers. For normal overclockers on stock cards a higher rating is better, but once you start using dry ice or liquid nitrogen, these are the cards you want.

During gaming we see the HD 7970 SOC sit right between the reference design and AMD's GHz Edition which uses increased voltage and runs at higher temperatures, both resulting in massively increased power draw.

Given the "Super Overclock" positioning of Gigabyte's card, I think the power draw numbers are acceptable if the card is able to provide better overclocking than other cards.

A new feature of the HD 7000 Series is AMD ZeroCore Power, which will power off the card as soon as the monitor output is blanked, during screen saver operation for example. For additional power and noise reduction, the fan will stop in this state, too. We measured a power consumption of 1.11 W for the whole graphics card during ZeroCore Power. As soon as you move the mouse the PC is back immediately; there is no lag or any delay.

Please note that ZeroCore Power seems to work only when the screen is completely static. If you have an application running that draws to the screen, the monitor will go black, but the card will not enter the low-power state or return from it quickly. To avoid this, minimize all applications and let Windows sit at the desktop.

NVIDIA has no competing technology to ZeroCore, so AMD is at a clear advantage here.