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Late 2015 iMac unable to boot into Mac OS X only boots Windows 10

A

alexlovesmacs

macrumors 6502a
Original poster
Apr 23, 2008
608
3
I have a 2015 iMac that has Windows 10 and it loads perfectly fine, I can watch 4K videos play games etc. So whenever I want to boot in OS X the progress bar fills but doesn’t load into OS X. I tried loading OS X from an external SSD and also transplanted my SSD from my 2009 Macbook Pro and it’s the same thing.

Today I tried target disk mode from my 2009 MBP onto the iMac to reinstall Mac OS and it is still stuck loading Mac OS. I am really tempted to erase the windows partition but scared that the iMac will be unusable with no working OS. Is there anything else I could do, I am thinking maybe the logic board needs replacing could that be it?
 
Boot with Command-V held down, and it'll give detailed output. Once it stalls, take a photo of the screen and post it here.
 
Nermal said:
Boot with Command-V held down, and it'll give detailed output. Once it stalls, take a photo of the screen and post it here.
Click to expand...
IMG_1848D.jpg
 
Are you able to load the recovery partition so you can reinstall from there? Tried resetting the smc and nvram?
 
bogdanw said:
No, it should work. Edit it only if your system volume has a different name than Macintosh HD.
Click to expand...
The volume is named Macintosh HD. Do you think I should try and delete the windows partition? Or anything else I could try?
[automerge]1586370326[/automerge]
Already tried resetting NVRAM and SMC still gets stuck at 100% loading screen. I am able only to access the iMacs hard drive on target disk mode on my MBP.
 
alexlovesmacs said:
Already tried it stays stuck at 100% at loading. Only way to access the iMac is through target disk mode on my MBP.
Click to expand...
Run the touch -c commnad from your MBP, be sure to write the correct path to the El Capitan installation.
 
I didn't suggest the command so I'm not sure, but I suspect you want to run it on the main partition. It looks like the command succeeded: There are no error messages in your latest photo.
 
alexlovesmacs said:
Tried it again and got this now. And am I supposed to do that on the recovery partition or the Macintosh HD? I did it on the recovery partition.
Click to expand...
You still got it wrong, you forgot / before Volumes
touch -c "/Volumes/Macintosh HD/System/Library/Extensions"
There is no confirmation message on success, but you can check if the prelinked kernel has been updated with
Code: 
ls -l /Volumes/Macintosh\ HD/System/Library/PrelinkedKernels/prelinkedkernel
or
Code: 
ls -l "/Volumes/Macintosh HD/System/Library/PrelinkedKernels/prelinkedkernel"
the date from the result indicating the modification date. Wait 10-15 seconds between the touch command and ls, to allow time for rebuild. Then reboot and try to boot with Command-V held down into El Capitan.
 
Ok so I just decided to wipe the hard drive. It loads into internet recovery mode then it just gets stuck at the black screen with Apple logo at 100%. I’m thinking there’s something wrong with the logic board.
 
alexlovesmacs said:
I have a 2015 iMac that has Windows 10 and it loads perfectly fine, I can watch 4K videos play games etc.
Click to expand...
alexlovesmacs said:
Ok so I just decided to wipe the hard drive. It loads into internet recovery mode then it just gets stuck at the black screen with Apple logo at 100%. I’m thinking there’s something wrong with the logic board.
Click to expand...
So, the logic board likes Windows, but not OS X? That doesn't sound logic to me :)
 
OP wrote:
"Ok so I just decided to wipe the hard drive. It loads into internet recovery mode then it just gets stuck at the black screen with Apple logo at 100%. I’m thinking there’s something wrong with the logic board."

DO NOT boot to the recovery partition.

INSTEAD, boot to INTERNET recovery. Do this:
- power down, all the way off
- press the power key and hold down "command-OPTION-R"
- if you are connected via wifi, you'll need your wifi password
- you should see the "spinning globe" while the utilities load -- be patient.

Does this work?
Do you get to internet utilities?
If so, do this:

Open disk utility.
Go to the "view" menu and choose "show ALL devices"
(if you don't see that choice, don't worry, just go to the next step)
Now, in disk utility, you need to click on the TOP LINE you see "on the left".
This is the physical drive inside the Mac.
Click it and then click "erase".

Now...
- if you're going to install Mojave or Catalina, choose APFS with GUID partition format.
- if you're going to install High Sierra or earlier, choose "Mac OS extended with journaling enabled", GUID partition format.
Then... erase the drive.

When done, close disk utility and open the OS installer and try again.

Last thought:
DON'T mess with bootcamp again.
If you need Windows, use an "emulated solution" such as VMWare Fusion, Parallels, Virtual Box, or perhaps even "Crossover" (which can run some Windows programs without actually installing Windows!)
 
I’m in the same boat. I’m going to try to replace the ssd in the iMac and see if that does anything.
 
I have a 2015 MacBookPro 15 that can't boot into Mac OS, not installed internally or to an external drive, nor internet recovery (CMD+OPT+R or CMD+OPT+SHIFT+R), even without any drive plugged it! It always results in boot loop EXCEPT when holding CMD+S to boot to a command prompt, which doesn't help me. CMD+V always reboots the scrolling text, so it's impossible to see where it is failing. Also already tried CMD+OPT+P+R reset 10+ times and SMC reset as many times.

I wiped the internal drive and I can't TDM install because the Mojave installer refuses to install to a TDM drive, so I borrowed another exact same MBP to reinstall and boot without issue, but the issue is still present in mine. Apple Store says it needs a $600 logic board replacement. I wish Seattle had a walk-in place like Louis Rossman to actually troubleshoot instead of just 'replace the logic board' option from Apple. I'm hoping I can install Windows on it to continue using it, or at least linux.
 
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