Power Consumption:

On top of our graphics performance testing, we have also measured the power consumption of AMD's ATI Radeon HD 3870 X2 graphics card at both idle and load. For this we used a slightly different test system, in order to keep the system the exactly the same across all of our power consumption measurements.

The system was configured as follows:

• Core 2 Duo E6750 (operating at 2.66GHz -- 8x333MHz)
  
• Gigabyte X38-DS5 motherboard (Intel X38 Express)
  
• 2 x 1GB OCZ FlexXLC PC-9200 memory (operating in dual-channel at DDR2-800 with 4-4-4-12 timings)
  
• Seagate Barracuda 7200.9 200GB SATA hard drive
  
• PC Power & Cooling 750W Silencer
  
• Windows Vista Ultimate x86

For our idle testing, we left the systems idling on the desktop for ten minutes, recording the average draw at the wall socket. For load testing, we used our benchmark routine from Crysis in DirectX 10 mode and measured the peak power consumption in this section of the title. We tested the cards in a number of other scenarios and this proved to be the most intensive in all cases, so you can consider this to be a worst-case scenario.

Bear in mind that we have disabled all CPU-related power management options in the motherboard's BIOS so that we can highlight exactly how well the GPU's power management features are working (or not).

For reference purposes, we also added the Radeon HD 2900 XT 512MB into the mix, even though we did not compare the card's 3D performance against the Radeon HD 3870 X2 -- in short, it's slower than the Radeon HD 3870 and there are full details on its performance characteristics in our HD 3870 review.



Once again, we see some impressive power consumption figures from AMD – the 3870 X2 is pretty frugal on the power when it’s running in idle mode and that’s all down to the ATI PowerPlay technology that the company implemented into its Radeon HD 3800 series hardware. Yes, G80 is still fabbed on a 90nm process, which is less efficient than if it was manufactured on 65nm, but what we have here today is a very power efficient dual-GPU solution.

You can see that at load, it consumes more power than any of the other GPUs, but the important thing to remember here is that a GPU doesn’t sit at full load 24 hours a day, seven days a week.