iM 4,1-14,4 iMac 21.5-inch, Mid 2011 white screen (of death?) while booting

[Laurent_de_Graff]

Hello everyone,

I'm new here so I hope I'm posting this in the right place.

I have an old iMac 21.5-inch, Mid 2011
2.5 GHz Intel Core i5
8 Go 1333 MHz DDR3
AMD Radeon HD 6750M 512 Mo
macOS High Sierra 10.13.6

One day it just started booting with no boot sound and the loading bar under not filling entirely before getting a white screen with nothing to do.

After some search on google I reset the mac PRAM NVRAM (with Option, Command, P, and R) which restored the mac booting sound but nothing else. Tried to reset the SMC but I have no idea if I've done it correctly or not

I tried booting into :

- Safe mode (holding shift) : white screen
- Recovery (command, R) : white screen
- Internet recovery (command, option, R) : Show the globe and loading bar gets to white screen before the end
- Hardware scan (D) : Boot fine into it, no problem detected by the scan
- Startup manager (Option) : Can choose between the main partition and the recovery : White screen on both
- Single User Mode (Command, S) : Boot fine into, tried the repair disk command (/sbin/fsck -fy) repaired something but didn't change the white screen problem

Now I tried creating macos recovery/install boot disk but since I don't have any other mac it was an ordeal, some USB weren't recognised some were but none got past white screen.

After that I made a Linux Mint live USB with Ventoy which I can boot into if I select GRUB2 mode then compatibility mode in the choices.
Linux Mint seems to run pretty fine with no problem whatsoever (I'm currently using this method to recover important files on the HD).

I found a thread (don't remember if it was here :s) which had really similar symptoms talked about dead (or malfunctioning) GPU and that a solution might have to be to force booting with the internal GPU but I found after that the thread were about macbooks and not iMac, I also read somewhere that those iMac absolutely not use integrated graphics I found other threads that say they do so I'm lost so I don't know who to trust.

Now with all this information what do you think I can do ?
Is there a way to recover/reinstall a macOS on this machine or should I (after recovering all important file) install another OS on it ?

I appreciate your help in advance,

LDG

 

[Nguyen Duc Hieu]

I guess your GPU is half dead.
On Linux Mint, try opening a Youtube video. If the machine freezes, it will confirm my assumption above.

 

[Laurent_de_Graff]

I guess your GPU is half dead.
On Linux Mint, try opening a Youtube video. If the machine freezes, it will confirm my assumption above.

Playing youtube video is fine, no freeze or anything

 

[CooperBox]

This post intrigues me. With a supposed dodgy GPU, why should this iMac boot and perform correctly with a Linux OS but not under Mac OS High Sierra. Is the former lighter on GPU demands, and if so why?
I have two 27" iMacs (2009 & 2011) held for spare parts, both with suspect GPU. What are the chances they will function if I install Linux Mint on the SSD's?

 

[Laurent_de_Graff]

Yeah I'm puzzled too

 

[Nguyen Duc Hieu]

So your GPU is not dead.
Now the second option:
1. Replace the internal disk with a blank SSD.
2. Do the Internet Recovery option
If Internet Recovery works, then the culprit is the old internal disk.

 

[Laurent_de_Graff]

So your GPU is not dead.
Now the second option:
1. Replace the internal disk with a blank SSD.
2. Do the Internet Recovery option
If Internet Recovery works, then the culprit is the old internal disk.

I don't have a blank SSD, but I have several HDD, what size does the iMac accomodate 3.5 or 2.5 inch ? (I guess I could see once I open it)

I don't know when I'll be able to do this as it is my mother's computer and she is the one recovering the files so it might take some time

 

[Nguyen Duc Hieu]

I don't have a blank SSD, but I have several HDD, what size does the iMac accomodate 3.5 or 2.5 inch ? (I guess I could see once I open it)

I don't know when I'll be able to do this as it is my mother's computer and she is the one recovering the files so it might take some time

The stock HDD is 3.5". But as they are all SATA disks, connection isn't an issue. A cheap 2.5" to 3.5" adapter is advisable to hold it it place and be stable.

 

[Laurent_de_Graff]

I have several 3.5" at hand, I asked because I only have two 2.5" and they're already in use in other computers.
I'll try to speed the recovery so I can test this soon.
Thanks for the help so far

 

[shloimy95]

if I select GRUB2 mode then compatibility mode in the choices.

With a supposed dodgy GPU, why should this iMac boot and perform correctly with a Linux OS but not under Mac OS High Sierra

So your GPU is not dead.

From experience Linux Mint on this model iMac starts with software rendering (llvmpipe) by default (and on any machine if started in compatibility mode).
You could check if this is the case by running

glxinfo | grep renderer

in terminal. If the output shows llvmpipe or LLVM it is using software rendering, in which case you have not tested the GPU.
If you get command not found install it by running

sudo apt install mesa-utils

then try again

 

[Laurent_de_Graff]

From experience Linux Mint on this model iMac starts with software rendering (llvmpipe) by default (and on any machine if started in compatibility mode).
You could check if this is the case by running

glxinfo | grep renderer

in terminal. If the output shows llvmpipe or LLVM it is using software rendering, in which case you have not tested the GPU.
If you get command not found install it by running

sudo apt install mesa-utils

then try again

I ran it and it does says llvmpipe in it.

Now on another note I tried a "windows to go" on another USB to try and have easier access to hfs+ partition on the hdd and on an external drive.
While it ran poorly it seemed mostly OK, I could also play YouTube video on it but I don't know if that helps in any way.

 

[shloimy95]

I ran it and it does says llvmpipe in it.

Now on another note I tried a "windows to go" on another USB to try and have easier access to hfs+ partition on the hdd and on an external drive.
While it ran poorly it seemed mostly OK, I could also play YouTube video on it but I don't know if that helps in any way.

So Linux Mint is using software rendering.
I don't really know how to check this in Windows, maybe someone more knowledgeable will answer. Is the Radeon GPU listed in Task manager? In device manager does it list it with a AMD driver (not Microsoft basic)?
In Google Chrome you could go to chrome://gpu to check if it is using hardware rendering. Possibly this (or edge://gpu) will work in Edge which is Chromium based, or you may want to install Chrome to check.

 

[Laurent_de_Graff]

So Linux Mint is using software rendering.
I don't really know how to check this in Windows, maybe someone more knowledgeable will answer. Is the Radeon GPU listed in Task manager? In device manager does it list it with a AMD driver (not Microsoft basic)?
In Google Chrome you could go to chrome://gpu to check if it is using hardware rendering. Possibly this (or edge://gpu) will work in Edge which is Chromium based, or you may want to install Chrome to check.

The driver was definitely microsoft basic

 

[Nguyen Duc Hieu]

So Linux Mint is using software rendering.
I don't really know how to check this in Windows, maybe someone more knowledgeable will answer. Is the Radeon GPU listed in Task manager? In device manager does it list it with a AMD driver (not Microsoft basic)?
In Google Chrome you could go to chrome://gpu to check if it is using hardware rendering. Possibly this (or edge://gpu) will work in Edge which is Chromium based, or you may want to install Chrome to check.

In Windows, we usually use the notorious Prime 95....
Or GPU-Z, perhaps...

 

[Laurent_de_Graff]

We have a "new" iMac (24i, M1) being delivered on monday, so I'll be able to put more time in troubleshooting the old one

 

[Laurent_de_Graff]

Hello everybody !

Life got in the way, I hope it's okay to necro my own post.

Since last time i did some testing and yeah GPU is definitely not doing okay.

Now I'm not particularly interesting in keeping the mac around with a linux install that might die any moment when the GPU kicks the bucket.
I've seen some video about converting old mac into plain monitor and that could be interesting as a replacement for my current second monitor on my windows setup which is an old phillips 190s (1280x1024)

Anyway if any of you can point me in the direction (name) of a compatible conversion (driver ? seen many names) board for my model I would be grateful.

Found this : "https://www.aliexpress.com/i/1005004680995735.html" for now but I have no idea if it's what I need

Thanks again for all your earlier help and the future,

LDG