I think I found the most easiest way to disable the 9600M GT of MBP5,1 (or any other one depending on MBP version) in EFI-Mode.
As you might know, the second card is still powered, even if you use the 9400M, and consumes some amount of energy, reducing the battery life.
Ok, here we go...
It's simple, isn't it?
echo 1 > /sys/bus/pci/devices/<pci_addr_of_card>/remove
Unfortunately it doesn't seem to work just with
since it says "Permission denied".
sudo echo 1 > /sys/bus/pci/devices/<pci_addr_of_card>/remove
will confirm that the device has been removed.
Of course, you can do this with most of the other PCI hardware as well.
To reactivate the removed devices, do a
I still have to verify the drop in the power consumption. What makes me suspicious is that the "NVIDIA X Server Settings" still show the second GPU, including temperature and clock frequency...
echo 1 > /sys/bus/devices/rescan
Please post if it's working for you or not.
Well, it seems not to have the effect I wanted to. At least not in EFI mode.
I checked the disabling strategy in BIOS mode (9600M GT only) by disabling the graphics device. It worked, the screen blanked. But immediately after that, the screen came back online, however spawning a console to log in. So something happens, but the graphis driver seems to enable the device again.
In EFI mode using the 9400M, when trying to disable the graphca, nothing happens. Although the device is not listed by "lspci" anymore. So I assume it doesn't work for the 9600M GT either.
Anyway, seems to go into the right direction...keep you posted.
Ok, just tested something. The problem is - oh my - related to the nvidia-drivers.
Here is what I did:
1) Boot in BIOS mode, with "nouveau" activated.
Do the "remove" trick.
-> Screen blanks (and stays so). System is still up (pommed still working; power-button and ENTER shuts down MBP).
2) Boot in BIOS mode, with "nvidia" enabled.
Do the "remove" trick again.
-> Nothing happens (but device is removed from output of "lspci").
Well, the nvidia-drivers have a different behavior in EFI mode than in BIOS mode. BTW, display backlight dimming doesn't work in EFI mode. And let me guess: Might have something to do with nvidia-drivers???