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AppleMacFinder

macrumors 6502a
Original poster
Dec 7, 2009
796
152
After disabling the dGPU using Arch, normal boot would hang halfway. Although safe boot would work. I wound up having to remove all the AMD kext files in the Terminal in Recovery Console.
Thank you for your report, dnewfield! Please tell me, do you have a clean display screen now? (screen that is not distorted by a failing discrete GPU) This information can be helpful to other people
 

lavrm

macrumors newbie
Mar 22, 2017
8
5
When I remove AMD kexts (no other fixes), it boots but no acceleration, everything is slow, graphic-demanding apps (including preview) not working. If I use gfxcardstatus in integrated mode, igpu works the same as dgpu with all acceleration, a bit slower but ok, even photoshop and premiere. After some days it either freezes or doesnt wake or kernel task gets 100% of cpu and hangs on reboot. After using both gfxcardstatus (2.1.1) and gpu-switch in integrated mode I get good quality boot screens and normal boot but after some days boot hangs on 40%, only safeboot is working. After PRAM reset I get distorted screen/gray screen with fans etc. again, and no safeboot. So I conclude that both GCS 2.1.1 and gpu-switch successfully write something to PRAM(NVRAM) but it does not prevent osx from trying to access dgpu in some situations, for instance, in google maps or any graphic demanding apps. Eventually I have come to using both apps simultaneously. But it all comes to an end unpredictably.
AppleMacFinder, please clarify:
1. Did you remove AMD kexts after your EFI variable fix? If yes, why did you remove them? dnewfield, after variable fixing and removing kexts, is there any difference in acceleration etc? Does your MBP work after your fix like after switching via gfxcardstatus? How graphic demanding apps behave?
2. Also I have studied the gpu-switch code, I found it almost the same as AppleMacFinder's commands and I wonder is there any difference between your fix and what gpu-switch does? It appears that gpu-switch works on my machine (good boot screen and after boot the about screen reports intel gpu) but osx still tries to access dgpu from time to time with sad results...
What dnewfield reports is very similar to my experience with gpu-switch and GCS 2.1.1.
 
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TitusVorenus

macrumors member
Mar 28, 2011
67
7
I used rufus rather than terminal, 100% ok! Thanks.

Now following this step:

"2) Boot to it:
insert this CD/DVD/USB to Macbook Pro, hold Option key while booting, choose "EFI boot" (that is your bootable installation media), press "e" key to edit the GRUB options of the Arch Linux archiso x86_64 UEFI CD menu entry while it is selected at the main screen, add nomodeset to the end of this line and press Enter. If everything is done correctly, you will find yourself at the Linux console!"​

When I do this, the result is the upper left of the screen says:

running early hook
blah
blah
blah
blah (udev)
Triggering events....

Then the screen fades to white from upper left to lower right, then either stays white or turns black, nothing else happens. What am I doing wrong?

[EDIT] After trying this 5-6 times, it shut off and the power button is no longer responsive.
 
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roberthallin

macrumors member
Oct 25, 2009
92
27
Stockholm, Sweden
Just wanted to report that my MBP is up and running! I went through the procedure so many times I can't be sure at what point it started working haha, but it went from being impossible to boot to working basically like it did before. Many many thanks for this AppleMacFinder.
 
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AppleMacFinder

macrumors 6502a
Original poster
Dec 7, 2009
796
152
Just wanted to report that my MBP is up and running! I went through the procedure so many times I can't be sure at what point it started working haha, but it went from being impossible to boot to working basically like it did before. Many many thanks for this AppleMacFinder.
Finally you have defeated this evil machine! ;) Humans are stronger than computers :D
Congratulations, roberthallin! Just one question: did you remove the AMD drivers from your MBP (as described in that 1st message) or they are still there? In theory this should not affect the end result, I am just curious
Did you remove AMD kexts after your EFI variable fix?
No, I removed AMD kexts before the EFI variable fix
If yes, why did you remove them?
Their removal was necessary to successfully boot the MBP (although with a sh!tty distorted graphics) . At this point of research I hoped that it is possible to just use gfxCardStatus to switch to "Integrated only", but it turned out that its impossible because of that "External display" (which in fact is internal) using the discrete GPU. Even after I have installed XCode and a bunch of other stuff (although the text was a bit difficult to see) to rebuild gfxCardStatus without a check for external displays, it still has not been able to work successfully. Only then, after researching it further, I have discovered this EFI variable fix - so when I did it the AMD drivers have already been removed (although in theory their removal should not impact the end results, the people could still try it to see if it helps)
dnewfield, after variable fixing and removing kexts, is there any difference in acceleration etc? Does your MBP work after your fix like after switching via gfxcardstatus? How graphic demanding apps behave?
This question is addressed to dnewfield but I will still reply regarding my experience... After doing that EFI variable fix with my MBP, all image goes from the working Integrated graphics, so a screen is completely clean (no distortions!) Even while running the graphic demanding apps, like the video games, Integrated graphics always remains in use - it is even impossible to switch to discrete GPU in gfxCardStatus when you are trying to do it on purpose! So far I have been surprised that one video game that I like - was playable at medium settings (although with a few lags sometimes). Mac's desktop also works almost perfectly, although there are a few lags as well - but these small lags are OK
is there any difference between your fix and what gpu-switch does?
If I understand it correctly, gpu-switch is aimed to switch the graphics after you have booted your MBP, even during the runtime - but in my case the gpu-switch was not working, probably because it tried to change the EFI variable at some later booting stage (either while login or during the runtime, depending on how you use it) , and this "External display" block - was already in action. So I reviewed gpu-switch code and used some notes from it to modify this EFI variable permanently with a correct value. And now my Mac is permanently on integrated graphics, it never tried to switch to discrete graphics even when I launched some video games
[doublepost=1490351196][/doublepost]
When I do this, the result is the upper left of the screen says:

running early hook
blah
blah
blah
blah (udev)
Triggering events....

Then the screen fades to white from upper left to lower right, then either stays white or turns black, nothing else happens. What am I doing wrong?

Hi TitusVorenus ! Please tell, in what mode did you write .iso file in Rufus? There are two modes in Rufus - ISO mode and dd mode. If you did it in ISO mode, I recommend creating a LiveUSB again in Rufus but this time in dd mode - so that it would be the same as if you would have created it from a terminal. Hopefully you added a SPACE character before the nomodeset option, to avoid it from merging with another boot option. Also, while the booting process should be quick, please wait at least 5 minutes - before deciding that it is stuck and forcing a reboot by holding the power button. If any other problems, reset your PRAM / NVRAM / SMC and then try booting again:
1) PRAM / NVRAM clean: https://support.apple.com/en-us/HT204063
2) SMC clean: https://support.apple.com/en-us/HT201295
After trying this 5-6 times, it shut off and the power button is no longer responsive.
Probably your battery is at low charge levels. Please charge your MBP before trying again,
and maybe its better to have it connected to a power adapter while you are trying all these instructions
 
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lavrm

macrumors newbie
Mar 22, 2017
8
5
AppleMacFinder, thank you for detailed answers! Just as a report: when I removed kexts (I simply removed all AMD*.kext in single user mode) the screen was distorted during boot but clear after login. It was soooo slow and many apps not working... And yes, not switchable by GCS. So I had to put kexts back -> no boot -> forced overheat shutdown -> boot on igpu -> switch via GCS 2.2.1 / gpu-switch -> reboot on igpu. That was my scenario, repeatedly used sometimes once in a week or so, sometimes almost every day after using photoshop or premiere). Now there is a great hope that it will be fixed more reliably! I will try to follow exactly your instructions on kexts removal and then EFI fixing.
 
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dnewfield

macrumors newbie
Mar 23, 2017
2
1
Thank you for your report, dnewfield! Please tell me, do you have a clean display screen now? (screen that is not distorted by a failing discrete GPU) This information can be helpful to other people

Yes, the display was clean after the efi mod in arch linux, but boot would stall at 50% until I removed all the AMD kexts. Everything seems to be working perfectly now (with slow graphics of course).

For the record, it's a MacBook Pro 15" early 2011, El Capitan.
 

TitusVorenus

macrumors member
Mar 28, 2011
67
7
Hi TitusVorenus ! Please tell, in what mode did you write .iso file in Rufus? There are two modes in Rufus - ISO mode and dd mode. If you did it in ISO mode, I recommend creating a LiveUSB again in Rufus but this time in dd mode - so that it would be the same as if you would have created it from a terminal. Hopefully you added a SPACE character before the nomodeset option, to avoid it from merging with another boot option. Also, while the booting process should be quick, please wait at least 5 minutes - before deciding that it is stuck and forcing a reboot by holding the power button. If any other problems, reset your PRAM / NVRAM / SMC and then try booting again:
1) PRAM / NVRAM clean: https://support.apple.com/en-us/HT204063
2) SMC clean: https://support.apple.com/en-us/HT201295
Probably your battery is at low charge levels. Please charge your MBP before trying again,
and maybe its better to have it connected to a power adapter while you are trying all these instructions

Ok, I made the change to dd mode in Rufus, added the space before nomodeset, and got to step 3! Somehow the full battery was used up, which was fast discharge, but now the machine is working again after plugging it back in. I also did the PRAM and SMC clean.

Now, I typed the following commands:

*) cd /
*) umount /sys/firmware/efi/efivars/ got the :(
*) mount -t efivarfs rw /sys/firmware/efi/efivars/
*) cd /sys/firmware/efi/efivars/

and I'm in:

root@archiso /sys/firmware/efi/efivars #


Is the next step to:

rm gpu-power-pre and then press TAB key for autocompletion

or

chattr -i "/sys/firmware/efi/efivars/"


?

Then follow with this exact text entry as stated in the guide?

*) printf "\x07\x00\x00\x00\x01\x00\x00\x00" > /sys/firmware/efi/efivars/gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9

*) chattr +i "/sys/firmware/efi/efivars/gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9"

*) cd /

*) umount /sys/firmware/efi/efivars/

*) reboot

Sorry for the step by step questions, I am a noob with command lines. I tried following the instructions further, but do not think I understood correctly, took a break after attempting the guide further, and the power cord dropped off and the machine ended up restarting. The machine no longer goes to the apple folder on normal restart, it now goes to a folder and "?".

I booted to archlinux again and now am at stage 3.
 

isolpa

macrumors newbie
Mar 25, 2017
1
1
I just signed-up to report that this method has worked on an once abandoned MBP with failing discrete graphics. I had been fiddling for a week before giving up with the similar solutions using grub, refit, clover... I was only able to disable the amd card but couldn't get the internal display to work. Anyways, this works! Kudos! I find it interesting that it didn't completely disable the AMD card since it still shows up on the system profiler. Before this I was using a combination of gfxCardStatus 1.8 and gpuswitch which seemed to enable integrated graphics but with many glitches related to still trying to use the discrete card. It was ok for browsing and basic tasks but couldn't use Photos app which was a waste of the otherwise working 15" screen. Thanks!!
 
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AppleMacFinder

macrumors 6502a
Original poster
Dec 7, 2009
796
152
Is the next step to: ... or ... ?
You need to follow the instructions at exactly the same order as they are described in my first message of this thread
Sorry for the step by step questions
If you have a trouble following this instruction, you could show this instruction to your friend who is more experienced with computers and ask for his help. However, I thought that these instructions are rather clear and easy-to-understand...
The machine no longer goes to the apple folder on normal restart, it now goes to a folder and "?"
In case the HFS+ filesystem of your MBP got corrupted, you could still try booting in a single user mode and repairing the filesystem; if it does not help, it is possible to repair it under Linux (like I have described at the 1st message) - a bit difficult, but definitely doable

After you'll have more questions, feel free to ask them
 
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TitusVorenus

macrumors member
Mar 28, 2011
67
7
You need to follow the instructions at exactly the same order as they are described in my first message of this thread

I tried again, I was just not sure of the linux feedback I was getting I think. It worked this time, the screen is normal!

In case the HFS+ filesystem of your MBP got corrupted, you could still try booting in a single user mode and repairing the filesystem; if it does not help, it is possible to repair it under Linux (like I have described at the 1st message) - a bit difficult, but definitely doable

I cannot boot to single user mode, I get the same grey screen with a "?" on a folder blinking. I am replacing the hard drive in this machine. I assume that's not going to help as this is now a firmware problem. Could you please help me identify which part of the first message contains the next steps I will need to repair this under Linux? I would give it a go on my own, but after reading the first post again 2 times just now, I am not confident I can pick out the proper section to follow.

BTW, I didn't think I could get this far. Thank you!!!!
 
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redrinus

macrumors newbie
Mar 23, 2017
8
5
Maybe you are doing something wrong, because Mac and Linux command lines are different... But here is easy workaround for you:
1) prepare a second USB drive, format it to FAT32 and plug it to your MBP together with a first USB drive (which contains Arch Linux)
2) after booting to Arch Linux, mount this second USB drive to some mount point, for example:
mount -t msdos /dev/sdXN /mnt/
where X is a drive letter, N is a partition number. If have some problems, search in the Internet for tutorials
3) copy gpu-power-prefs-... file to this second USB drive, unmount it, plug it to another PC and view the contents of file with a hexdump
This is a normal message, I have been getting it even on the "not-yet-changed" Mac...
So this error does not indicate that your MBP feels this variable change. There should be some visible changes, like MBP's screen becoming normal again while booting! If there are no visible changes after changing the EFI variable, it means that somehow the EFI variable has not been loaded and we accidentally did something wrong...

By the way you could try completely removing the AMD drivers from your MBP - this is described at my first message. Of course that will not fix a display of your Mac, but at least it will boot every time. And (although unlikely) this may somehow impact your success with EFI variable
[doublepost=1490299287][/doublepost] If you have the problems with terminal, you could just find a PC with windows and use Rufus utility to create Arch Linux bootable USB - https://rufus.akeo.ie/ , https://wiki.archlinux.org/index.php/USB_flash_installation_media#Using_Rufus . It is really straightforward


Almost. if=input device or file (in this case, ISO file) . of=output device or file (in this case USB drive) . So you also need to choose a correct path to your USB drive. "of" value is VERY IMPORTANT, because if you accidentally choose a Macbook's HDD device path instead of USB drive device path - that will screw up your partition table and you can lose all your data from Macbook's HDD !

So, if you never worked in a terminal before, I recommend you to just find a Windows PC and use Rufus, for your own safety
Hi AppleMacFinder,

I mounted a USB stick under Linux (FAT32) and mounted the /sys/firmware/efi/efivars following your procedure. From this point, I cannot copy the gpu-power file to the USB stick. It keeps telling me:

cp: error reading 'gpu-power-pref-xxxxxx': Invalid argument (xxxxxx represents all the numbers....)

Actually, I cannot do anything with the file. "mv" or anything else gives the same error. Remember that I could not do the hexdump either with the file for the same reason. There are no trailing spaces in the file name.

What is going wrong here? There seems to be something with the filename? It is not the USB stick, since copying this gpu file to another file to the same location does not work either...

Thanks for your help.
 

AppleMacFinder

macrumors 6502a
Original poster
Dec 7, 2009
796
152
It worked this time, the screen is normal!
I'm very happy about your success ;)
I cannot boot to single user mode, I get the same grey screen with a "?" on a folder blinking. I am replacing the hard drive in this machine.. Could you please help me identify which part of the first message contains the next steps I will need to repair this under Linux?
You have two options now:
1) If your screen is normal now, that means you can boot to OS X Installation DVD/USB now - and it has Disk Utility, using which it could be possible to repair your filesystem
2) Or, alternatively, you could do these steps:
Remove a hard drive from MacBook Pro and (using a USB to SATA 2.5" adapter) attach it to a computer with Linux, then follow these instructions:

https://superuser.com/questions/961401/mounting-hfs-partition-on-arch-linux (1st answer) - carefully execute a number of commands, calculate a sizelimit for your parition layout, and finally run sudo mount -t hfsplus -o force,rw,sizelimit=YOURNUMBER /dev/sdb2 /mnt to mount this HFS+ partition to /mnt directory in read-write mode. Then you repair a filesystem by running sudo fsck.hfsplus -f /dev/sdb2 before unmounting a partition with sudo umount /mnt and putting a hard drive back to MBP...
But for that you need a spare computer with Linux installed or Linux LiveCD launched (preferably Ubuntu LiveCD, for beginners in the Linux world...) , and as you can see its a bit lengthy process, so hopefully you could avoid it with "1)"
[doublepost=1490550651][/doublepost]
I cannot copy the gpu-power file to the USB stick. It keeps telling me: cp: error reading 'gpu-power-pref-xxxxxx': Invalid argument (xxxxxx represents all the numbers....
I am not sure why you can't copy this file, weirdly it acts like it is a write-only... To be honest, I never tried copying or hexdumping this file before, because in my case this fix worked from the first time. Sadly its impossible to teleport to you and debug these problems together, but I wish you all the best and believe that after a few more attempts you will fix your MBP
 

lavrm

macrumors newbie
Mar 22, 2017
8
5
I have successfully done the fix, it’s working like a charm!
I am so happy after three months of trouble!
AppleMacFinder, thank you, thank you, and thank you!!!

Some comments, maybe helpful for others:

1. Unmount and remount /sys/firmware/efi/efivars/ in rw mode was necessary.

2. chattr -i "/sys/firmware/efi/efivars/" did not work (error: Inappropriate ioctl for device while reading flags on /sys/firmware/efi/efivars). So I suppose that it is a mistake in the instruction. Used chattr -i "/sys/firmware/efi/efivars/gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9" instead (first -i to remove the file, then after prinf with +i to protect it).

In all other respects everything went fine!
 
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TitusVorenus

macrumors member
Mar 28, 2011
67
7
Thanks AppleMacFinder!

This solution did indeed work for me, and I as a command line noob I was able to get everything working properly and have got my 17in MBP up and running again! As a noob, I encountered some problems, so I'm going to post the steps I followed here which will hopefully allow other noobs to get 'er done faster.

1) Create the Arch Linux LiveCD/LiveUSB in Rufus in dd mode (see post 55 in this thread)

2) Boot to it: insert this CD/DVD/USB to Macbook Pro, hold Option key while booting, choose "EFI boot" (that is your bootable installation media), press "e" key to edit the GRUB options of the Arch Linux archiso x86_64 UEFI CD menu entry while it is selected at the main screen, add (a space and then) nomodeset to the end of this line and press Enter.

3) Edit EFI vars: looks like efivarsfs filesystem is mounted by default! So you can already cd /sys/firmware/efi/efivars and ls to explore this directory and see if there is a "gpu-power-prefs-..." variable (where ... is UUID of this variable). If there is such a variable, its better to remove it with rm.

At this point, I referenced this post and followed these instructions, because when i didn't I got no results.:

@CarefreeCanadian I esperienced the same problem using an Ubuntu Live 16.10 distribution and I solved the issue with the following steps:

To remove “gpu-power-prefs-..." variable it is necessary first of all to unmount efivars:

*) umount /sys/firmware/efi/efivars/

then mount efivars in read/write mode:

*) mount –t efivarfs rw /sys/firmware/efi/efivars/

*) chattr -i /sys/firmware/efi/efivars/gpu-power-prefs-[press TAB to autocomplete]

*) rm /sys/firmware/efi/efivars/gpu-power-prefs-[press TAB to autocomplete]

At this point I continued following AppleMacFinder's instructions (part 3):

*) cd /
*) umount /sys/firmware/efi/efivars/
*) mount -t efivarfs rw /sys/firmware/efi/efivars/
*) cd /sys/firmware/efi/efivars/

*) chattr -i "/sys/firmware/efi/efivars/"

*) printf "\x07\x00\x00\x00\x01\x00\x00\x00" > /sys/firmware/efi/efivars/gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9

*) chattr +i "/sys/firmware/efi/efivars/gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9"

*) cd /

*) umount /sys/firmware/efi/efivars/

*) reboot

This switched to integrated graphics on boot. However something happened to my hard drive (commentary earlier in this thread). I was not able to reinstall OSX properly with the drive in the computer, so I had to pull it and reinstall. Then, I updated OSX after reinstalling the hard drive and the integrated graphics stopped working.

The OSX updates with the hard drive installed reversed the changes I made in Linux.

So I went through the process again to switch to integrated graphics full time. Then I pulled the hard drive and reinstalled OSX with all updates. I reinstalled the hard drive (now an SSD) and it's working faster and cooler than it ever has before!
 

lavrm

macrumors newbie
Mar 22, 2017
8
5
By the way, it seems that after the fix dgpu remains powered: my battery time decreased from ~5 hrs to ~3 hrs ceteris paribus. Also I have somewhat more heat on the underside.
 
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TitusVorenus

macrumors member
Mar 28, 2011
67
7
By the way, it seems that after the fix dgpu remains powered: my battery time decreased from ~5 hrs to ~3 hrs ceteris paribus. Also I have somewhat more heat on the underside.
I have significantly less heat on the underside.
 

Sanpete

macrumors 68040
Nov 17, 2016
3,695
1,665
Utah
Is it guaranteed the dgpu will go bad like many original xbox 360 and nvidia chips from 2008ish. My wife has one and it work perfectly fine but I may replace it before the inevitable.
Well, sure it's guaranteed to fail eventually, like every other bit of hardware, but if it's still working fine, why replace it?
 

AppleMacFinder

macrumors 6502a
Original poster
Dec 7, 2009
796
152
Is it guaranteed the dgpu will go bad like many original xbox 360 and nvidia chips from 2008ish. My wife has one and it work perfectly fine but I may replace it before the inevitable.
As you can see by my case, even if discrete GPU worked for 6 years - it does not guarantee that it is fault free. Aside from the batteries/keyboards, which ARE replaceable by user (with some efforts), this GPU is probably the next thing in the list that is going to fail. If having a working discrete GPU is a requirement for your activities, and you got a spare $35, you might buy this replacement chip in advance - ( http://www.aliexpress.com/item/DC-2...0028-216-0810028-BGA-Chipset/32764872143.html or https://www.aliexpress.com/item/DC-2015-New-216-0810001-216-0810001-Graphic-Chipset/32718112928.html , because don't know if this is true - https://www.rossmanngroup.com/board...0604-replace-216-0810005-gpu-with-216-0810028 ) - in advance, its' supplies will not last for forever... Otherwise, just bookmark this instruction, keep enjoying your discrete GPU while it lasts, then after it will fail - switch to integrated graphics with this EFI variable fix
 
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Bwil10

macrumors newbie
Mar 31, 2017
19
14
Hi everyone,

Been using these forums for a while so thanks to all for being really very helpful.

It seems my Mac is fairly bricked, GPU failure on a late Mac 2011.
Apple offered to extend the repair program but once it got to the raptor shop they decided they couldn't help.

I've read that the GPU can be replaced, but the people I've called locally don't seem to think this will fix the problem.

I should note that I don't get any garbled screen or text, but it hangs or turns grey.

What I'm trying to do to get the Mac to bypass the GPU and only use integrated, right?

I tethered booted to another machine and used a program gfx-something to only use the integers GPU but I suspected that wouldn't work.

I found your thread and it seems really useful but in single user mode it won't grant me write privileges, any ideas?

Im not very good at this type of type, and unix is something i know nothing about.
 

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GnarlyVoid

macrumors newbie
Mar 31, 2017
2
2
First up, big big thanks to AppleMacFinder for creating this solution, and to those others who have helped progess it.

I have an early 2011 MBP 17" with a fried graphics card as of mid-January, so it's been good to get it back. In my case, I could boot into Single User Mode. I could also boot into OSX proper when in SMC Debug mode, but the constantly roaring fans did my head in, so once I had all my files backed up, away it went. This mode bypasses a lot of things, including the discrete graphics card. However, programs could still call the dGPU, causing a freeze, requiring a hard shutdown. I soon lost the ability to boot into my Snow Leopard partition, but could still boot into my El Capitan (10.11.6) partition.

I was delighted to find a firmware fix, so went about applying it. Enduring the fans, I prepared the bootable Arch installer.

To clear the SMC Debug mode I did an SMC reset, followed by a PRAM reset. Being curious, I immediately booted into the Arch installer to see what was in my NVRAM. Turns out, all 3 GPU- ... variables were gone, as was the gfx-saved-config-restore-[GUID]

QUESTION: Based on that, would it be safe to experiment with different values for these GPU variables (using printf), on the basis that I can clear the NVRAM of those values if the display fails to come up? Or is there a risk of bricking the firmware?


My first attempt failed to finish booting. I (belatedly) recalled that Snow Leopard wasn't booting, so I booted into Single User Mode (which showed it was the Snow Leopard partition was now the default boot) and applied:

/sbin/fsck -fy

It gave the result that the Volume appears OK, as well as "The volume was modified". Conventional wisdom says keep running fsck until it doesn't give the "Volume was modified" message. The next fsck gave the all clear, so it was:

shutdown -h now

to get out of Single User Mode (note: typing "exit" will cause the normal boot process to occur, which I didn't want.)

I booted into the Arch installer as per instructions.
I re-mounted the efivarfs as read/write
As there was no gpu-power-prefs-[GUID], I created it with printf, then made it immutable
Unmounted, then rebooted.

This first boot was rougher than the Millenium Falcon jumping into hyperspace - to get to the login screen took just over 2 minutes (versus around 30 seconds when things were good) - but it finally made it!

Woo-hoo! I have an almost-fully-functional MBP!

ALMOST?

Well, one thing I didn't do is move the kexts out and re-build the kext cache. Again, I was curious. Here are the consequences:

1) Energy Savings Pane in System Preferences still has "Automatic Graphics Switching" available and selected.
2) Playing or even previewing any movie file causes freeze, requiring a hard shutdown. Fortunately, the EFI fix seems persistent, as I was able to boot up again.
3) Safari will work OK, until some website video will call on the dGPU, causing a freeze etc.
4) Firefox has been fine, as I've switched its "Hardware Acceleration" option off.
5) Although the fix survives a hard shutdown, it curiously did not survive a Restart from the login screen. I'm not sure if something went wrong that one time, or if it's something peculiar to my setup, or if the Restart process itself reliably causes this.

I applied the same steps again (including first going into Single User Mode to fsck the Snow Leopard. Again, it found something to modify). It worked first time through. Still haven't kicked the kexts out. Later.


My conclusion is that, with the kexts still in place, setting the gpu-power-prefs- as per this guide (and as per SwitchGPU?) doesn't strictly disable* the dGPU. Rather, only the iGPU is enabled and the dGPU is not enabled during the boot process, but the OS is still aware of the dGPU (Graphics Switching in System Preferences), and programs can try to use it later (and crash the MBP).

*Strictly disable:
1) dGPU is powered off
2) OS is not aware of it
3) dGPU cannot be invoked/used/poked.

What are your thoughts on 1) ? Does this process also power off the dGPU? (Is such a state even possible?)

My experience is that in Single User Mode, and in Arch installer, my MBP heated up (quickly, and substantially) at the left rear (magsafe - Esc key area). With the gpu-power-prefs altered, there's a slight warmth, but only where it is resting on a stand. So I would say my dGPU is not powered up.

As for 2) and 3), currently, moving out the kexts (plus the EFI fix) as per this guide is the way to go.

My wishlist would be to just edit the EFI variables to achieve all 3, but it seems that the relevant information (of how to do it - indeed, of "is it even possible?") is unavailable or well hidden.

It's been fun


PS This was posted as a Reply to a few posts, but due to a wardrobe malfunction, I didn't actually Quote and respond to those posts. Doh! Apologies to all
 
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GnarlyVoid

macrumors newbie
Mar 31, 2017
2
2
Hi everyone,

Been using these forums for a while so thanks to all for being really very helpful.

It seems my Mac is fairly bricked, GPU failure on a late Mac 2011.
Apple offered to extend the repair program but once it got to the raptor shop they decided they couldn't help.

I've read that the GPU can be replaced, but the people I've called locally don't seem to think this will fix the problem.

I should note that I don't get any garbled screen or text, but it hangs or turns grey.

What I'm trying to do to get the Mac to bypass the GPU and only use integrated, right?

I tethered booted to another machine and used a program gfx-something to only use the integers GPU but I suspected that wouldn't work.

I found your thread and it seems really useful but in single user mode it won't grant me write privileges, any ideas?

Im not very good at this type of type, and unix is something i know nothing about.


Hi Bwil10,

This is indeed a really useful thread for those of us suffering dGPU failure in our MBPs.

From what I've read, at some point in the boot sequence, some process calls the dGPU, which fails to respond, at which point the boot process hangs. Grey screen and lamentations follow.

So we want the dGPU to be totally ignored, always, and only have the iGPU being used.

The method posted here is the only method I've found that achieves this aim.

I found that gfxCardStatus wasn't useful when the dGPU has already failed. When I was running my MBP in SMC Debug mode, I installed gfxCardStatus. It showed I was on Dynamic Switching. When I selected "Integrated Only", my MBP would freeze, and a hard shutdown was needed. I concluded that the dGPU was being "called" in some way (even though I was switching away from it), crashing the MBP in the same way playing a video, or launching iMovie, would crash the MBP.

I was curious about the GPU being replaced - can you elaborate on that?



And now, a warm welcome to the Command Line Universe!

If you are totally new to using Command Line Interfaces (CLI), my best words would be to double check what you type, before you press Enter. (I can get a bit OCD about long entries, and sometimes check them 3 or 4 times, and even then still make a typo).

Spaces are important. For many commands, the only consequence is that nothing happens other than a message. For some commands, a space in the wrong place, or the wrong number of spaces, can have middling to dire consequences (like wiping your entire hard drive).

Googling a command can be quite helpful - you can find out how it has been used, what it can't do, and what disasters people have had with it.


When you are in the CLI itself, you can always bring up a manual about a command by typing:

man [command]

e.g. to get info about the shutdown command:

man shutdown

Typically, pressing q will quit you out of the manual and put you back to the command prompt. For more info about manuals, type:

man man



It was good you posted the pic. There is one space missing in the mount command (after uw):

/sbin/mount uw/

Should be:

/sbin/mount uw /


With that you should have read/write privileges, and from there move the kexts etc.

I also see that fsck has modified the volume. It's a good idea to run fsck again until it doesn't give you "the volume was modified" message. It doesn't always pick up every problem the first time it runs.


Finally, I love the idea of a raptor shop. I want one. A shop, that is, full of raptors. Cheers
 
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AppleMacFinder

macrumors 6502a
Original poster
Dec 7, 2009
796
152
I've read that the GPU can be replaced, but the people I've called locally don't seem to think this will fix the problem
That will not fix a problem ONLY if you "repair" it at Apple, because Apple will just replace your faulty motherboard with another faulty motherboard but which is not showing a problem, yet... So Apple's fix is a temporary fix

I know there are affordable solutions like $50 BGA resoldering at unofficial local repair shop and that its possible to get a new replacement HD 6750M chip from AliExpress for $35 or cheaper ( http://www.aliexpress.com/item/DC-2...0028-216-0810028-BGA-Chipset/32764872143.html ) to guarantee a successful repair, so the total price of repair would be either $50 or $50+$35=$85 - less than $100 in any case. But I don't like investing money to the old computers, so I have thought - what if there is some hack to force MBP to use integrated graphics ALL THE TIME, even while booting ? And then started to explore the possible solutions...
^^^ This hardware fix is a real fix, not Apple's "fix", but it requires spending the money - and, if you don't need the discrete graphics for your activities, better to go with this software solution of disabling the failed discrete graphics permanently - which is described in this guide

What I'm trying to do to get the Mac to bypass the GPU and only use integrated, right?
Yes, this solution is a permanent switch to integrated GPU, to make your MBP bootable and work OK

used a program gfx-something to only use the integrated GPU but I suspected that wouldn't work
Yes, gfxCardStatus can not be used for the permanent switch to integrated only. That is why this solution has been created

in single user mode it won't grant me write privileges, any ideas?
Most likely that means your HFS+ filesystem is slightly corrupted and that is why no write permissions. Looks like you have to repair your HFS+ filesystem before going forward.

Use fsck -fy command to repair your filesystem, and at your command from screenshot - mount -uw / - you forgot to write a SPACE character before / (you wrote mount -uw/ , should write mount -uw / )
[doublepost=1491132264][/doublepost]
Would it be safe to experiment with different values for these GPU variables (using printf), on the basis that I can clear the NVRAM of those values if the display fails to come up? Or is there a risk of bricking the firmware?

I believe that if you use the wrong value of that GPU gpu-power-prefs-... variable, it will either not work or will act as one of the defined behaviors (dynamic switching / integrated only / discrete only) which are described at this file - https://github.com/0xbb/gpu-switch/blob/master/gpu-switch Even if you somehow mess up your other EFI variables (on purpose? ;)) and make your MBP unbootable, it should be possible to reset their values with PRAM/NVRAM/SMC resets

My conclusion is that, with the kexts still in place, setting the gpu-power-prefs- as per this guide (and as per SwitchGPU?) doesn't strictly disable* the dGPU. Rather, only the iGPU is enabled and the dGPU is not enabled during the boot process, but the OS is still aware of the dGPU (Graphics Switching in System Preferences), and programs can try to use it later (and crash the MBP).

OS is still aware of the dGPU, yes, but it will be impossible to even enable it manually with gfxCardStatus. Even when I launch some graphics-demanding applications like the video games, MBP is NOT switching from integrated to discrete. So this software fix of permanently switching to integrated GPU - is quite reliable

*Strictly disable:
1) dGPU is powered off
2) OS is not aware of it
3) dGPU cannot be invoked/used/poked.

From your list, I am confident that 3) works OK , but not sure if 1) or 2) are possible. 1) dGPU is powered off - even while you are at this Integrated only mode, the discrete GPU still will consume some power (although the small power) because of the hardware design 2) OS is not aware of it - OS will always be aware of it because the discrete GPU is connected to CPU through the PCI lines, so OS will always notice this discrete GPU - but it will never be able to use it because of this software EFI variable fix

What are your thoughts on 1) ? Does this process also power off the dGPU? (Is such a state even possible?)

My experience is that in Single User Mode, and in Arch installer, my MBP heated up (quickly, and substantially) at the left rear (magsafe - Esc key area). With the gpu-power-prefs altered, there's a slight warmth, but only where it is resting on a stand. So I would say my dGPU is not powered up.

Please see above

As for 2) and 3), currently, moving out the kexts (plus the EFI fix) as per this guide is the way to go.
Even if you remove the kexts, that GPU will still be visible to CPU through PCI lines, and will be slightly powered because of the hardware design

I was curious about the GPU being replaced - can you elaborate on that?
Probably he has been referring to:

I know there are affordable solutions like $50 BGA resoldering at unofficial local repair shop and that its possible to get a new replacement HD 6750M chip from AliExpress for $35 or cheaper ( http://www.aliexpress.com/item/DC-2...0028-216-0810028-BGA-Chipset/32764872143.html ) to guarantee a successful repair, so the total price of repair would be either $50 or $50+$35=$85 - less than $100 in any case. But I don't like investing money to the old computers, so I have thought - what if there is some hack to force MBP to use integrated graphics ALL THE TIME, even while booting ? And then started to explore the possible solutions...
I am confident that this hardware fix will work, because this is a real fix, not an Apple "fix" (replace a faulty motherboard with another faulty motherboard which just is not showing a problem yet) But probably its not a good idea to invest the money to old computers unless you desperately need that discrete graphics for your activities
 
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