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.

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 3DMark03 Nature as a standard test representing typical 3D usage because it offers: - very high power draw - high repeatability - is a standard benchmark that is supported by all cards - drivers are actively tested and optimized for it - supports all multi-GPU configurations - easy to obtain - fairly compact in size - test runs a constant duration and renders a non-static scene with variable complexity just like any normal game.

The four result values are as following:

• Idle: Windows Vista 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: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. This results in the highest power consumption. Average of all readings (12 per second) while the test was rendering (no title screen).
• Peak: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. 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.
• 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.

Just like the other HD 6900 Series cards, the HD 6990 comes with AMD's PowerTune technology. In a nutshell this technology constantly monitors different sections of the GPU for abnormal high load conditions and clocks down the card in such a case. This serves as a protection feature to avoid overcurrent and overheating during applications like Furmark.

Another power saving feature is called "ULPS", which disables the inactive slave GPUs in CrossFire when the card is in 2D or when playing back video content. However, ULPS is an overclocker's nightmare. Due to the way the technology is implemented, it will cause most overclocking utilities to crash the system when they try to access the second card which is "off".

In terms of power consumption we see pretty high numbers across all tests. ULPS does help a little bit, but personally I think the gains are too insignificant to be worth all the overclocking problems. Overall power consumption is high, but roughly in line with what could be expected from a single-board dual-GPU card in this performance class.

A decent power supply is a must for the Radeon HD 6990, I would recommend something from 800 W upwards, depending on the rest of your system.