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.


In order to characterize a video card's power consumption, the whole system's mains power draw was measured. This means that these numbers include CPU, Memory, HDD, Video card and PSU inefficiency.

The three result values are as following:

• Idle: Windows sitting at the desktop (1024x768 32-bit) all windows closed, drivers installed.
• Average: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. This results in the highest power consumption. Average of all readings (two per second) while the test was rendering (no title screen).
• Peak: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. This results in the highest power consumption. Highest single reading

NVIDIA has implemented a load of power saving features in the GT200 graphics processor:

• Hybrid Power: When used with certain nForce motherboards the graphics card can be fully disabled with 2D graphics output coming from the onboard graphics chip. When switching to 3D, the GPU will be turned on seamlessly.
• Clock Gating: Certain unused parts of the chip can be turned off until they are needed.
• GPU Load detect which switches clocks and voltage on the fly. Yes you read correctly, the 2D/3D clocks are back. The following table describes the different settings the card can run at.
  
  

  	2D Idle	Video Playback	3D Performance
  Core Clock	300 MHz	400 MHz	576 MHz
  Memory Clock	100 MHz	300 MHz	999 MHz
  Shader Clock	600 MHz	800 MHz	1242 MHz
  GPU Voltage	1.03 V	1.06 V	1.12 V

  The load detection is not dependant on 3D fullscreen, but on actual GPU usage. Some earlier products had the problem that they would run in 2D mode only even when a windowed 3D application was active. This is not a problem on the GTX 260.

Overall NVIDIA has achieved great idle power consumption, together with the GTX 280 these cards set new standards for high-performance cards in idle, look at how far ATI's HD 4870 is away. Under load the GTX 260 can also show its efficient design, claiming performance per watt leadership as we will see on the summary graphs a bit later on.