This blog post is based on upgrading an external SSD installed on my Big Sur disk (using Patched Sur on my unsupported iMac 27 inch late 2013 – iMac 14.2) to macOS Monterey.  Please note, this does not cover all unsupported Mac devices.  The reason I use an external USB connected SSD disk is that I need multiple macOS environments to test various issues my clients are having.  Also, I do not want to install unsupported macOS on the internal disk of my iMac 27 inch late 2013.  Please also note that Apple does not like a Mac computer having multiple profiles (one machine starts up from different macOS), so please do not connect to iCloud except for the macOS you use for your main production environment.  (After starting up Mojave, Big Sur and Monterey by swapping the startup disk and each time I reconnected iCloud, my Apple ID password was disabled for a security reason – according to Apple)  I had to reset the password while going through a tedious process not mentioning I had to change the Apple ID password for all the other Apple devices including my iPhone and iPad).

As to a genius BenSova’s Patched Sur, please refer to my previous blog post link below.  It covers the latest macOS Big Sur 11.6.7.

Apple Myth 13 – How to install macOS Big Sur (11.2) on unsupported Mac devices

The end result for my macOS Monterey unsupported iMac 27 inch late 2013 is the following images.

Monterey 12.4 running on unsupported iMac

Monterey 12.4 running on unsupported iMac

Monterey Software Update

Monterey Software Update

My iMac 27 inch late 2013 is enrolled in the Apple Developer Program (happened a long time ago).  OpenCore Patcher disguises Apple where unsupported Mac devices can still get the latest macOS updates.  macOS 13 Beta is the next version of macOS Ventura.  If I click Upgrade now, then my OpenCore patched Monterey system will be destroyed.  I will post on my next blog post regarding the next macOS Ventura in conjunction with the OpenCore patcher.

Monterey Developer Update

Monterey Developer Update

Being involved with the Apple Developer Program, my iMac 27 inch late 2013 also showed the Monterey Developer update before the public Beta test.  However, I’ve decided not to apply any Beta updates as I’m using Monterey with my unsupported iMac on my main production Mac and taking the Automatic Update option off.  I will wait until the public release of Monterey 12.4 to get to version 12.5.


Starting from macOS Monterey 12.5 Beta 3 update, Apple has taken away Graphic Card Acceleration support for Nvidia GPU known as Nvidia Kepler (Like my iMac 27 inch 2013 with Nvidia GeForce GTX 780M 4GB – iMac 14.2).  The latest Monterey 12.5 public release updates the system, but once OpenCore Legacy Patcher applies root patch then restart the system, it goes into login loop and the Mac computer becomes unusable.  Recommendation for an unsupported Mac computer with Nvidia Graphic Card should stay with Monterey version 12.4.

For more details, please visit the following Macrumors Forum

macOS 12 Monterey on Unsupported Macs Thread

Part I. Basics

Which Macs can run macOS 12 according to Apple? (Monterey)
12-inch MacBook (early 2016 and later)
MacBook Air (early 2015 and later)
MacBook Pro (early 2015 and later)
Mac mini (late 2014 and later)
iMac (late 2015 and later)
iMac Pro (2017 and later)
Mac Pro (late 2013 and later)

But OpenCore Patcher opens the door for older Mac computers to run macOS 12 Monterey.

Please take a look at the following links before you start. Although video clips are relatively old, they still stand out as a great source of information.

Thank you to a very talented Mac Specialist Mr. Macintosh.

a. How to Upgrade from Big Sur to Monterey & Update OCLP OpenCore Legacy Patcher – Unsupported Mac!

b. Monterey on Unsupported Mac [2008-2015] OpenCore Legacy Patcher!!!

c. Create a Bootable macOS Monterey USB Installer IN 5 MIN!!!

Part II. OpenCore Legacy Patcher

You should always keep up to date with the OpenCore Legacy Patcher.  Please download the latest version from the following link.

OpenCore Legacy Patcher

Part III.  What I did

a. Using an external Patched Sur (Big Sur) installed SSD to start up the system.  (I used Super Duper! to clone the original Big Sur external disk)

b. Downloaded OpenCore Legacy Patcher

c. Started OpenCore Legacy Patcher and updated EFI of the Big Sur installed disk

Install OpenCore on an external Big Sur SSD disk

Install OpenCore on an external Big Sur SSD disk

Choose External 1TB Big Sur Installed SSD

Choose External 1TB Big Sur Installed SSD

d. Created standard Monterey installable USB 3 stick (16GB)

Full installer download link (ver 12.4)

(If you would like to download the above full package, please copy paste the above link in a new tab.  Otherwise, download will not start )

Once the full InstallAssistant.pkg download was complete, I simply ran the package program and chose the External 1TB Big Sur Installed SSD and the installer application was placed in the Applications folder.

Connected an USB 3 stick with at least 16GB capacity.

Then ran the terminal program;

sudo /Applications/Install\ macOS\ –volume /Volumes/”Name of the USB Stick”

e. Restarted the system holding alt key whilst connecting to the USB stick with Monterey installer.

Chose the EFI loading button then started the USB stick base Monterey installer.

Everything went well successfully upgraded Big Sur to Monterey.  After that, all I had to do was to apply Post-Install Volume Patch under OpenCore main menu and updated Nvidia Graphic Card drivers and restarted the system.

Post-Install Volume Patch

Post-Install Volume Patch

I did not create OpenCore EFI installed USB 3 installer stick (I did it afterwards).

Part IV. Patched Sur vs OpenCore

Biggest benefit to using Patched Sur (Big Sur) is cloning with Super Duper!  Whilst OpenCore installed the external disk cannot be cloned with SuperDuper! (Carbon Copy Cloner also fails).  I’m still looking for software which can clone OpenCore installed on to an external disk as I do not use the Time Machine backup (waste of time).

Biggest benefit to using OpenCore installed Monterey is the version update.  It can be updated even for an incremental update (not a full update) just like an ordinary Mac computer. But make sure you check before any updates that the OpenCore Patcher is the latest version.


OpenCore team just released ver 0.4.7.  GUI interface application only ( and no more Terminal base application is available.

OpenCore Legacy Patcher

Replaced 0.4.6 Terminal application with ver 0.4.7.  Updated EFI partition and applied system volume patch.  It’s working fine.


Apple Developer Program released macOS Monterey 12.5.  It appears OpenCore Legacy Patcher (current version is 0.4.8) does not support this version as yet. (I tested with my unsupported iMac 27 inch late 2013).  After the macOS update, if I apply Root Patch by OpenCore Legacy Patcher, after the restart I cannot login to the system and it goes into login loop.  I created Monterey testing environment on a separate USB attached SSD.  The current OpenCore Legacy Patcher works up to Monterey 12.5 Beta 2 (I have not yet tested Beta 4), but Beta 5 and this 12.5 (appears to be final – not as yet released to the public) will fail to start up.  So, you’d better wait until OpenCore Legacy Patcher supports Monterey 12.5.

macOS Monterey 12.5 Beta2

macOS Monterey 12.5 Beta2

macOS Monterey 12.5

macOS Monterey 12.5


Opencore Legacy Patcher team released version 0.4.9 where the team acknowledge the issue with a Mac has Nvidia GPU.  In the release note, the team say “Warning for Macs with Nvidia Kepler: macOS 12.5 breaks graphics acceleration with this build”.  The team further say “Stay on 12.4 or older if your Mac has a Kepler GPU. 0.4.9 will prevent the installation of Kepler acceleration patches, instead only installing basic framebuffer in 12.5. macOS 12.4 and older are not affected, and can still be used normally.”

If you need help for Mac computers  (Sydney CBD, Sydney North Shore – particularly in Carlingford, Epping, Chatswood, Roseville, Lindfield, Killara, Gordon, Pymble, Turramurra, Wahroonga, Warrawee, Hornsby, Macquarie Park and St Ives area) please contact Harry 0417 424 909.  Or refer to our Service page.

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