How to protect native EFI when installing Windows 11 since OpenCore Legacy Patcher does not work on T2 iMac?

[timidhermit]

I recently learned that I cannot use OpenCore Legacy Patcher (OCLP) on an iMac Pro I had just purchased in used condition to use to dual boot to macOS and Windows because of the T2 chip in this iMac.

Long ago, I have been advised to always install OCLP when I want to install Windows 10/11 in a Mac, regardless whether or not BootCamp is being used initially to help to create the Bootcamp partition to where Windows will be installed. This is done so to protect the native EFI from being altered by Windows as OCLP will create its own EFI partition which Windows can modify to create the dual boot.

Since I cannot install OCLP in my iMac Pro, is there another alternative way to "protect" the native EFI without using OCLP so to mimic OCLP's function to create a separate EFI partition to use for the dual boot? Alternatively, is this still necessary for this generation of iMac as compared to very old generations of Macs (like MacPro4,1 and MacPro5,1)?

Given that BootCamp does not natively support Windows 11, must I use BootCamp to first install Windows 10 and then do an in-place upgrade to Windows 11?

 

[joevt]

What's in your EFI partition?

I have a Mac mini 2018 with T2 chip. The built-in SSD EFI partition has a EFI folder with a APPLE folder and a UPDATERS folder. Apple uses these for firmware modification or updating? The actual boot loader is stored on the Preboot partition or the System partition.

If you're worried about the EFI partition, make a copy of it before installing Windows.

 

[timidhermit]

What's in your EFI partition?

I have a Mac mini 2018 with T2 chip. The built-in SSD EFI partition has a EFI folder with a APPLE folder and a UPDATERS folder. Apple uses these for firmware modification or updating? The actual boot loader is stored on the Preboot partition or the System partition.

If you're worried about the EFI partition, make a copy of it before installing Windows.

Joevt,

Thanks for the advice. I was told that the EFI partition gets modified over time by Windows, particularly whenever Windows is updated. Supposedly, the worry is that excessive modification can randomly corrupt the EFI and make the machine unbootable. Even if the actual boot loader is not affected, I was told that this can make the machine UNRECOVERABLE even when the system is put into recovery mode to reinstall the macOS. This in effect "bricks" the system permanently.

As implied above, I am not sure if such advice is still applicable to newer Intel iMac such as the iMac Pro. That is why I am asking. I owned a MacPro5,1 (cheese grader). and I saw plenty of YouTube videos advising on using OCLP when installing Windows in order to protect the EFI (not just for upgrading to a newer macOS that the system does not natively support).

Appreciate any clarification you can give me on this. I am very murky on this issue despite having read through many threads on here and on Reddit.

 

[chrfr]

Joevt,

Thanks for the advice. I was told that the EFI partition gets modified over time by Windows, particularly whenever Windows is updated. Supposedly, the worry is that excessive modification can randomly corrupt the EFI and make the machine unbootable. Even if the actual boot loader is not affected, I was told that this can make the machine UNRECOVERABLE even when the system is put into recovery mode to reinstall the macOS. This in effect "bricks" the system permanently.

As implied above, I am not sure if such advice is still applicable to newer Intel iMac such as the iMac Pro. That is why I am asking. I owned a MacPro5,1 (cheese grader). and I saw plenty of YouTube videos advising on using OCLP when installing Windows in order to protect the EFI (not just for upgrading to a newer macOS that the system does not natively support).

Appreciate any clarification you can give me on this. I am very murky on this issue despite having read through many threads on here and on Reddit.

That issue was really particular to the older Mac Pros, not with newer computers.

 

[bogdanw]

I don't think Windows modifies the EFI partition if macOS was first installed. Windows creates its own reserved partition.

 

[startergo]

Windows modifies its bootmanager. Since it is called bootx64.efi and a regular opencore boot loader is called the same if they are on the same EFI partition and in the same folder layout Windows expects it may override it on update/upgrade. OCLP normally installs its boot loader in a different folder structure than Windows expects and it is called boot.efi. So OCLP getting overritten by Windows is practically impossible. Not sure why OCLP does not work on T2 Macs but I have used Opencore on T2 Macs without a problem

 

[timidhermit]

Windows modifies its bootmanager. Since it is called bootx64.efi and a regular opencore boot loader is called the same if they are on the same EFI partition and in the same folder layout Windows expects it may override it on update/upgrade. OCLP normally installs its boot loader in a different folder structure than Windows expects and it is called boot.efi. So OCLP getting overritten by Windows is practically impossible. Not sure why OCLP does not work on T2 Macs but I have used Opencore on T2 Macs without a problem

Can you share more specifics about your particular T2 Mac(s) running OCLP? Which Mac(s)? Which macOS? Which OCLP (are you using a special forked version)? Are you able to then use BootCamp or some other methods to install Windows as well?

My understanding is that this has been a longstanding issue with OCLP incompatibility with T2 Macs. You are the first I read on this forum who said to be running T2 Macs on OpenCore without any issue. Please kindly share. 🙂

 

[startergo]

I used OpenCore not OCLP in the past on MacBookPro15.1 and MacMini2018. I used it for specific reason to be able to boot a Bootcamp external ssd so I did not have to fake any SMBIOS settings.