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.

In ATI's latest GPU you will see new improvements to their PowerPlay power reduction features. A special microcontroller is integrated into the ASIC now which controls all aspects of power saving. Basically it gets fed a table with clocks, voltages, fan speeds and when to apply them. Just like previous generations the card switches performance levels depending on GPU load, the new features allow better control over it though.


Looking at the clocks table above I can simply describe it with one word, "fail". Why all those great power consumption features if the memory clock and GPU voltage isn't reduced when the card is idle? That's what this feature is for.

The load detection is not dependent 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 the case on the HD 3xxx and HD 4xxx Series.

Even though ATI has all these shiny new features the idle power consumption of the HD 4870 is very high, NVIDIA's GTX 280 which offers much more performance uses over 40W less. Under load the relative power consumption fits better to the performance class the card offers, yet NVIDIA seems to be doing better here as well with their GTX 280. Still, the HD 4870 does not require a nuclear fusion reactor to power, any half-decent modern PSU with two PCI-E power connectors should be able to run it perfectly stable.