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.

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.

The VTX3D HD 7870 Black is based on the higher-spec Tahiti graphics processor instead of the regular Pitcairn. It is good to see single-monitor idle power consumption remain unchanged, as most systems will run for extended periods of time in that state.

Multi-monitor power consumption is pretty bad - just like on the other HD 7900 Series cards. If you plan on using a multi-monitor productivity setup all day at work, you might want to consider this added power cost as it's quite significant, being almost twice as high as that of a regular HD 7870 and three times as high as comparable NVIDIA cards.

Gaming power consumption is much higher as well. The HD 7870 is a very efficient design, so the VTX Black with its Tahiti processor doesn't do well. Looking at performance per watt, the design is just as efficient as the HD 7970 GHz Edition, which means these two cards are the least efficient of AMD's current lineup.

Tahiti LE based graphics cards are definitely not the best choice if you care about power consumption.