I'd like to disable the NVidia GTX 750M GPU on my MacBook Pro 15" (Retina, Mid 2014, Mac OS X 10.10 Yosemite). I know I can use GfxCardStatus but I read I could have a more permanent solution by changing some EFI flag.
My question is:
-
How can I disable the discrete GPU from EFI?
I assume this is persistent across multiple reboots. I'd also want to know how to undo it if needed.
Update:
The question is basically whether the command mentioned in GfxCardStatus github issue comment here is correct or not, and how to undo it if it doesn't work.
.
An answer to this alone is a correct answer, but it'll be awesome if you can also tell me:
-
If you force integrated graphics in GfxCardStatus, Mac OS X (up to Yosemite at least) doesn't allow you to use multiple monitors (even though the built in Iris Pro can do it).
If I disable the discrete GPU from EFI, will macOS think that the integrated GPU is the one installed and will it let me use multiple monitors with it?
-
I heard that the same EFI setting is responsible for not even showing the integrated GPU to other operating systems than macOS and you have to trick it somehow to think it's macOS.
Is that true? And if yes, how to do that?
Best Answer
You can permanently disable discrete graphics card following next steps:
UPDATE! Try to edit NVRAM variable from Single-User mode
The procedure described in the steps 1-3 worked for me until macOS Sierra, but with the upgrade to High Sierra, I started getting a pinkish/reddish screen and I was unable to enter Recovery mode to repeat step 3 as I had to do in previous upgrades. Searching in internet, I stepped into this GitHub issue explaining you may be able to replace steps 1 and 2 with the following command, that you can execute in Single-User mode (boot pressing cmd+s):
1. Prepare a Bootable USB pendrive with a non GUI Linux
1.1 Download ArchLinux ISO
1.2 Creating the bootable USB with the .iso
Open /Applications/Utilities/Terminal in MacOS and list all storage devices:
diskutil listYour USB device will appear as something like
/dev/disk2 (external, physical). Verify that this is the device you want to erase by checking its name and size and then use its identifier for the commands below instead of/dev/diskX.A USB device is normally auto-mounted in macOS, and you have to unmount (not eject) it before block-writing to it with dd:
diskutil unmountDisk /dev/diskXNow copy the ISO image file to the device. The dd command is similar to its Linux counterpart, but notice the 'r' before 'disk' for raw mode which makes the transfer much faster:
sudo dd if=path/to/arch.iso of=/dev/rdiskX bs=1mAfter completion, macOS may complain that "The disk you inserted was not readable by this computer". Select 'Eject'. The USB device will be bootable.
2. Use Linux to change EFI vars
2.1 Boot to it
nomodesetto the end of this line and press Enter.2.2 Clear existing EFI vars
Looks like efivarfs filesystem is mounted by default! So you can already
cd /sys/firmware/efi/efivarsandlsto explore this directory and see if there is agpu-power-prefs-...variable (where ... is UUID of this variable).If there is such a variable, it's better to remove it with rm.
rm gpu-power-prefs-…If you are getting the "operation not permitted" message while attempting to
rm, it means that efivarfs has been mounted as read-only and you need to remount it with read-write permissions and try again:cd /umount /sys/firmware/efi/efivars/mount -t efivarfs rw /sys/firmware/efi/efivars/cd /sys/firmware/efi/efivars/rm gpu-power-prefs-…If this also fails (you still can’t erase the file), use
chattrcommand to disable file immutability and then erase the file:chattr -i "gpu-power-prefs-…”rm gpu-power-prefs-…2.3 Create a new gpu-power-prefs-… file
2.4 Add immutability to the gpu-power-prefs-… file
This
chattrcommand is supposed to lock a file to make it accessible only by "superuser" - and so that, while booting, your EFI will have no chance to screw up your gpu-power-prefs-... variable under any circumstances2.5 Unmount efivars and reboot
Change to the root directory to unmount efivars:
Guarantees that your EFI variables are flushed to efivarfs filesystem. Please unmount it safely before rebooting.
3 Remove AMD / NVIDIA kexts
Note: You might need to do this every time you update your OS, since it normally regenerates these kexts. You may want to favourite this answer for reference so it is accessible from another device when you need it.
After disabling the dGPU using Arch, normal boot would hang halfway but safe boot will work.
3.1 Move AMD / NVIDIA kext files to a backup directory
Remove all the AMD (or NVIDIA, depending on your card) kext files in the Terminal in Recovery Console. Trying to remove them in Single User just gives sandbox errors, so don’t do it in Single User Mode! (the one that you boot with cmd+s).
Start Terminal (This commands are for AMD. If you have NVIDIA, change accordingly)
diskutil cs list(find Logical Volume UUID: last item)diskutil coreStorage unlockVolume UUID(UUID: from previous command)cd /Volumes/Macintosh\ HDmkdir AMD_Kextsmv System/Library/Extensions/AMD*.* AMD_Kexts/rebootI found the procedure in this link, where you can read the attribution of the different sections and a discussion thread on the topic.
I tried it myself on an early 2011 MacBook Pro with a faulty discrete graphics card, that was unable to boot even with the overheating trick, and ended up with a fully functional computer!