View Full Version : Power consumption when idle

12-19-06, 01:44 AM
All CPUs have ways of lowering the power consumption when they are idle. For example, modern Intel CPUs have SpeedStep which lowers the clock and sends HLT command to decrease the power drain. AMD also has similar systems. Even if the CPU doesn't support it, you can run third party programs to send the CPU HLT commands when idle.

I've never come across and article that tells about such a feature in GPUs. I'm concerned that when I'm at my job, my PC at home is on downloading things and wasting power. CPU goes into low power mode, but GPU does not. I suspect even when my monitor is turned off and I'm away, my nvidia card is going at it full force like I was playing Oblivion.

Does anyone know anything about this? Do the video cards save power when they are idle? Is there a program that sends HLT command to the GPU when idle?

12-19-06, 02:21 AM
No, in 2D it uses less power for sure. There were tests for this from several review sites and the difference between 2D and 3D was 100w if not more IIRC.

Of course a 8800GTX is still using plenty of power even in 2D mode, but donīt forget that you have a card here with a GPU with over 680 million transistors at 90nm (C2Ds dont even have 300 million at 65nm), and 768MB of RAM and that one needs some power as well.

12-19-06, 02:58 AM
I don't understand why we need to have a GPU running at all when the monitor is off. Monitors are plug and play and support ACPI, so the operating system can check if the monitor is on or off.

Simple logic: If monitor is off, the user can't see squat. Therefore, video card is not needed. So, shut it off. When the monitor is turned on, turn the video card on too.

I suspect it isn't so simple, or it would be implemented. So, why isn't it so simple?

12-19-06, 04:49 PM
Well, there is an ACPI mode (S3 or S4) which turns off the video card as well. Iīm the wrong person to ask about the details because I never used any hibernate or ACPI mode. When I donīt use my computer I turn it off and Iīm done with it. :)