iATKOS | United Kingdom

Ok I just want to give you a heads up about this issue I had and how to fix it, I hope this can help someone that is having the same problem in the present or in the future for reference.

So here is the deal, I was using my iMac 5K 2015 with OpenCore on macOS Sequoia, it worked ok but the startup times were pretty bad and some slows downs here and there, so after like 9 years of use and no new 5K iMac being released anytime soon I finally decided to pull the trigger and get a Mac Mini M4 Pro with a Studio Display, so the iMac got stored in a storage room and never used for some time.

After some time I decided to bring back the iMac and put in another room to give it some use to that amazing 5K screen, so when I turn it on to my surprise it was the infamous black screen with the support.apple.com/mac/startup at the bottom, so I did what I know and even more to restore this Mac but nothing worked, so I decided to see whats going on with the Fusion Drive, this iMac came with one PCIe blade SSD and one HDD, mixed together were the Fusion Drive, so after some more tests the PCIe blade SSD was randomly unresponsive until it was fully unresponsive, I guess the drive was finally done, so I decided to separate the disks and just install everything in the HDD but the only thing that worked was restoring to the very first macOS version that came with the iMac from the factory, macOS El Capitan, so after that I updated to macOS Monterey and it fails, it keeps stuck at some % and restarted and again the same thing, it was a infinite loop, I searched a lot about this issue and what I find is that the dead PCIe blade SSD was causing all the issues, I had to remove it but I didn't want to open this iMac because it is pain in ass to remove the screen and put it again, and read a lot of horror stories about after some days the screen will randomly fall out and crack!

So I decided to buy an external usb SSD drive and try to install the last supported macOS version for my iMac (Monterey), and let me tell you, it was extremely hard to do it, the damn PCIe blade SSD was still causing a lot of issues, every restart was with some new error, but I got a pattern, it was something like this: Boot from a USB installer to install to the external SSD, then restart to error, hard restart again to another error, hard restart to continue install, then restart to error, hard restart to another error, then hard restart and continue install, and so many times more, this was extremely tricky but it fucking worked!! I was able to install Monterey to the external drive and it worked way faster than before, I tested the speed of the disk and the internal HDD would get 200 mb/s and the external usb ssd would get almost 500 mb/s.

Now I decided to clone my external disk to the internal HDD just in case as a backup, so I used Carbon Copy Cloner with the Apple Recovery option selected and boom it cloned the whole disk installation and I was able to finally boot from the internal drive to macOS Monterey.

Of course I wanted more so I did everything to update from Monterey to Sequoia using OpenCore and I was able to upgrade the external usb SSD disk and boot to Sequoia, everything was working great and better than before without having to risk my iMac opening it, but still there was one issue left, the boot time took like 4 to 5 minutes!! so I enabled verbose mode to see whats going on and yes of course the damn PCIe blade SSD was the culprit, macOS was trying to load the drive 3 times with 60 seconds timeouts (busy timeout[0], (60s): APPLE SSD SM012BG Media) so thats 3 to 4 minutes of my time wasted with macOS trying to communicate with a dead drive, so I remember I was booting using OpenCore so maybe I could make a patch to completly ignore the drive, so thats what I did and it worked!! instead of booting in 4 to 5 minutes now it boots in less than a minute, sometimes in 40 seconds!!

So if you having the same issue here is how I did the patch:

1. Locate EFI partition diskutil list

2. Mount EFI partition (if your AFI partition is disk0s1) sudo diskutil mount /dev/disk0s1

3. Open EFI files open /Volumes/EFI/EFI/OC

4. Backup EFI files cp -a /Volumes/EFI/EFI/OC ~/Desktop/OC-backup-$(date +%Y%m%d)

5. Find the correct SSD controller from the dead SSD ioreg -p IOService -r -c IOPCIDevice -l > ~/pcitree.txt

   Open the pcitree.txt file and search: For AHCI blades: class-code" = <01060100> and look for an acpi-path under .../_SB/PCI0@0/RPxx@.../(SSD0|AHCI)@0 For NVMe blades: class-code" = <01080200> and look for acpi-path under .../RPxx@.../(SSD0|NVM|NVME)@0

   Convert the acpi-path segments to OpenCore: Each @DD,FF → Pci(0xDD,0xFF); single @DD → Pci(0xDD,0x0)

   Prefix with PciRoot(0x0) Example: .../RP17@1b,0/SSD0@0 → PciRoot(0x0)/Pci(0x1B,0x0)/Pci(0x0,0x0)

6. Open /Volumes/EFI/EFI/OC/config.plist

7. Add this under DeviceProperties / Add

    <!-- Patch to disable faulty internal SSD on boot for iMac 5K 2015 --> <key>PciRoot(0x0)/Pci(0x1B,0x0)/Pci(0x0,0x0)</key> <dict> <key>class-code</key> <data>AAAAAA==</data> <key>device-id</key> <data>AAAAAA==</data> <key>IOName</key> <string>disabled</string> </dict> <!-- End --> 

   The full DeviceProperties will look something like this:

   <key>DeviceProperties</key> <dict> <key>Add</key> <dict> <key>PciRoot(0x0)/Pci(0x1c,0x0)/Pci(0x0,0x0)</key> <dict> <key>brcmfx-country</key> <string>US</string> </dict> <!-- Patch to disable faulty internal SSD on boot for iMac 5K 2015 --> <key>PciRoot(0x0)/Pci(0x1B,0x0)/Pci(0x0,0x0)</key> <dict> <key>class-code</key> <data>AAAAAA==</data> <key>device-id</key> <data>AAAAAA==</data> <key>IOName</key> <string>disabled</string> </dict> <!-- End --> </dict> <key>Delete</key> <dict/> </dict> 

8. Save file and unmount EFI partition (if your AFI partition is disk0s1) sudo diskutil unmount /dev/disk0s1

9. Reboot and boot with OpenCore

10. If you ever update OpenCore files you will need to patch this again

The most tricky part of this patch is finding the correct SSD controller key that you need to put in so LLMs are your best friends to help you get the exact value, just give them the pcitree.txt and tell them to help you find the right value that you need and format it for OpenCore.

Hope this post help someone out there in the present or the future when their internal ssd drives finally dies and don’t want to risk opening their iMacs, using an external SSD drive is a great option for older Macs.

I want to thank the OpenCore devs and community that makes this amazing software to be able to bring back old Macs and gave them another live, thank you so much!!

BTW the external usb SSD drive I got was a Kingston XS1000, I love that it is extremely small so I can hide it behind the iMac in the back of the stand and it looks pretty slick, the drive could get to 1000 mb/s but it depends in your USB ports.