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Modern video cards seem to use 150-200 Watts at idle. Does this mean that this is the minimum power the video card will ever draw while your computer is on? It's clear that if you are sitting at the Windows desktop and not doing much, this is the power you'll be drawing. If you're playing a game, you'll draw more power. But what about when your computer is idle long enough to trigger Windows' "Turn off the display" event? Will the video card use negligible power during this time, or still use idle power?

To be clear, I am not talking about the entire computer entering sleep or standby mode. I'm also not talking about simply pushing the power button on the monitor. I'm talking about the computer being on, visible on the network, possibly performing background or server tasks, but with the display off as a result of Windows power settings.

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Does the Windows' "Turn off the display" have anything to do with the video card ? – sdadffdfd Mar 24 '11 at 14:23
I love Anandtech, but I feel obligated to point out that those are high-end gaming video cards you link there. I have a machine across the room with a bitchin' card that uses 12 watts at idle; it just won't play Crysis. – Shinrai Mar 24 '11 at 14:40
Those aren't GPU power usage numbers in the chart. It is the power usage for the whole system at the wall. To get to GPU power usage you need to take into account the loss of AC to DC conversion and then the power usage of the rest of the hardware. – Mr Alpha Mar 24 '11 at 14:51
@victor23k Yes, it does, because Windows achieves this by telling the video card drivers to kill the display output. And, as I've experienced, if you have buggy versions of nVidia drivers, you can run into situations where turning off the display does not work properly (or you can have it garbled when it comes back on). – Greg Mar 24 '11 at 15:32
@MrAlpha - You're right. But, today's CPUs use 15W at idle, power supplies are 80% efficient, and whole systems can use 25-50W at idle, so the graphics card is far and away the largest portion of the power shown. – Greg Mar 24 '11 at 15:35
up vote 3 down vote accepted

Many modern cards usage very low power when idle for example my sapphire hd5770 consume 18w when idle and 108w when at its max. i don't comment on any specific card but commonly new cards consume less power during idle state. And even if window turn off the display it can not turn off the gpu and video ram. there will be very low or nothing difference between idle and display off state.

there is one exception. when you have hybrid sli(onboard and discrete graphics running in sli mode) then windows can completely turn off the discrete graphics card like 9800 gx2. you find this kind of setup more in notebooks where you can turn off the gpu.

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That very much depends on the graphics card in your system.

I can only find this for certain relating to ATI Radeon graphics cards.

Some graphics cards do have a 'low power' mode where they reduce their power consumption considerably when they activate DPMS (Display Power Management Signaling).

From the Linux Radeon manual page:

Option "DynamicPM" "boolean"
      Enable dynamic power mode switching.  This can help reduce  heat
      and  increase  battery  life  by  reducing  power usage when the
      system is idle (DPMS active). The default is off.

I don't believe anyone has done a negative power consumption test - all the tests I have found have been while running the cards at maximum. It would be an interesting project to test various cards in running, idle and DPMS modes.

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Power consumption of the graphic card depends on the application being used. Switching the monitor off will not effect the power consumption of the graphic card. For example, if I run a game, and switch off the monitor, still the graphic card would be providing the resource to the game even after the monitor is switched off. The only thing that will slow down the graphic card is the application being used.

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