Power Consumption:

On top of our graphics performance testing, we have also measured the power consumption of AMD's ATI Radeon HD 3870 512MB 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).



There are a number of things we can draw from the results we've obtained here. The first being that AMD's power management technologies are more advanced than Nvidia's at the moment, saving around 16W of power at idle. Meanwhile, when the GPUs are running at load, the system consumes roughly the same amount of power at the wall, which suggests that both AMD's and Nvidia's maximum TDP numbers are in line with one another.

What's most impressive about the Radeon HD 3870 though is just how much power the Radeon HD 2900 XT consumes in comparison. At idle, the now discontinued 2900 XT consumes almost 60W more power than the 55nm RV670-based card. It doesn't stop there either, as the Radeon HD 2900 XT consumes about 100W more power at load too -- that's an incredible power saving for what is essentially the same performance (if not slightly higher).