ZOTAC GeForce GT 640 2 GB

ZOTAC GeForce GT 640 2 GB

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.
Single-monitor idle power consumption of the GT 640 is comparable to similar offerings in the lower end segment.

In multi-monitor and Blu-ray playback the card profits from NVIDIA's latest driver changes which enable the card to single-monitor clock speeds, which makes additional power savings possible. As a result the card is one of the most power efficient options if you want to build an eco-friendly non-gaming system.

Gaming power consumption is very reasonable too, but the card doesn't offer much in terms of gaming power, so these numbers are only of secondary importance here.

One missing feature on NVIDIA Kepler based cards is AMD's ZeroCore power, which basically turns off the card when the monitor is switched off, resulting in a power consumption of around 1 W. The NVIDIA card will consume full idle power in that case. This might be an important point for office systems that do not get turned off overnight. Or media PC systems that are always on to provide storage/background downloading, yet are not actively used.

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