How can I disable a PCI or USB device (including the video card)?

cyberic · 2012-12-25 16:22:47

Hi

I'd like to save some power and reduce the heat of my fanless barebone (an atom-based arctic mc001, see here;
http://www.amazon.fr/gp/product/B005DL6 … 5DL6V8G%22
It consumes 25W idle, and gets a bit hot.
So I'd like to disable some of the devices I don't use.
For instance:
- the internal wifi dongle (appears in lsusb)
- the internal TNT tuner (appears in lsusb)
- the internal DVD drive
- the internal radeon graphic card

For all of these devices, I do a "echo 1 > unbind" in sysfs, for the correct devices.
After that, all these devices seem 'disconnected' IE they no t not appear anymore in lsusb or lspci (for the radeon)
I also put the USB ports in 'auto' power mode

After that, the devices do not generate any IRQs or wakeups anymore, according to powertop...
But the power consumption does not decrease a lot... less that 1W...

So I wonder if the fact to unbind the devices really disconnects them or not.

Especially for the radeon... shouldn't I underclock it as much as possible instead? If so, how?

Thanks for your help.
Eric

runny6play · 2012-12-25 17:03:42

I can't really help you much but to give you a warning. underclocking/undervolting too much can damage a video card without your knowledge, if your going to underclock it make sure you do stabilty tests. Your also gonna need it for any graphics environment you may want if your processor doesn't have one, unless your going command line only. you can try seeing if disabling it with rf-kill does anything. you can also use iwconfig to turn on power saving on your wifi-card, and try adjusting your cpu scaling as well. logically I would'nt worry about the dvd if heat is our concern a dvd drive in standby is proably not going to be throwing off a lot of heat or use very much power.. the big players are probably going to be your cpu, gpu and maybe that wifi card I know when mine is in use it just drains the battery with out power-saving. as for the tuner I have no idea. I hope this post can give you some ideas and maybe move you in the right direction. I can't garentee that all of this is accurate, some of it is logical assumptions. just trying to throw out some ideas to help a fellow arch -linuxer

cyberic · 2012-12-29 22:51:05

Thanks for yuor answers, runny6play.
I won't need my graphic card at all, my server will be headless.
For the dvd, I know it won't generate heat, but maybe interrupts, so disabling it will mean (maybe) slightly less heat
For the internal wifi dongle, I think that 'unplugging' it will be even more efficient than 'rfkill'ing it, but I'm not sure....

Does anyone has anything to add?

Thanks
Eric

karabaja4 · 2012-12-30 00:12:10

cyberic wrote:

Does anyone has anything to add?
Thanks
Eric

I do...

1) Most (or all) mainboards will refuse to boot without a functional graphics card, POST will fail. So you cannot disable it.

2) I don't think you can damage your graphics card by undervolting/downclocking. I am not 100% sure so better do a bit of research or wait for someone to confirm.

cyberic · 2012-12-30 01:45:19

I know I can't disable the graphc card, it is soldered directly.....
But I think I might be able to "unbind" it from the PCI bus after booting

Arch Linux

#1 2012-12-25 16:22:47

How can I disable a PCI or USB device (including the video card)?

#2 2012-12-25 17:03:42

Re: How can I disable a PCI or USB device (including the video card)?

#3 2012-12-29 22:51:05

Re: How can I disable a PCI or USB device (including the video card)?

#4 2012-12-30 00:12:10

Re: How can I disable a PCI or USB device (including the video card)?

#5 2012-12-30 01:45:19

Re: How can I disable a PCI or USB device (including the video card)?

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