AMD Radeon HD 7970 3 GB Review 301

AMD Radeon HD 7970 3 GB Review

Fan Noise »

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. 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 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 Crysis 2 as a standard test representing typical 3D gaming usage because it offers: - very high power draw - high repeatability - is a current game that is supported on all cards due to its DirectX 9 nature - drivers are actively tested and optimized for it - supports all multi-GPU configurations - test runs a 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) all windows closed, drivers installed. Card left to warm up in idle until power draw is stable.
  • Multi-Monitor: Two monitors connected to the tested card, which use different display timings. 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: 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 stress test until power draw converged to a stable value. On cards with power limiting systems we will disable the power limiting system or configure it to the highest available setting - if possible. We will also use 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 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.
Power consumption of the AMD Radeon HD 7970 is impressive.

The move from 40 nm to 28 nm itself promises reduced power requirements. Then AMD also worked on technologies that improve power consumption through various methods.

Idle power consumption, which matters for normal desktop work, has seen a substantial improvement, going down to 12 Watts, which is about where you would see last-generation's lower-end cards. Unfortunately multi-monitor power consumption has not received such big improvements. 45 W when running two or more screens, seems like a lot, considering single monitor power draw is down to 12 Watts now.

For gaming we see spectacular values, especially with performance taken into account. The HD 7970 consumes 20 W less power, yet is over 30% faster than the last generation HD 6970. This ensures that the card claims a leading spot in our performance per Watt ranking.

Blu-ray media playback power is a bit high at 53 W. During testing I noticed that the card went into a lower power state of around 40 W every few seconds, but jumped out of it almost immediately. With some additional tweaking I'm sure AMD can get this fixed.

A new feature of the HD 7900 Series is AMD ZeroCore Power, which will power off the card as soon as the monitor output is blanked, during screen saver for example. For additional power and noise reduction the fan will stop in this state, too. We measured a power consumption of 1.11 Watts 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 engage 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.

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