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Preventing Win10 Upgrade from Writing to Clover EFI, Any Suggestions?


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I'm overdue for a major upgrade to my Win10 installation (Dual boot: Mojave on the NVMe card, Win10 on a SATA SSD), but due to my slow internet, it's more convenient for me to do a "upgrade in place" with the Win10 installer ISO downloaded elsewhere. The problem is I want to avoid some problems that I had experienced with my previous Hackintosh (Yosemite and Win7 on separate HDDs).

I want to prevent Win10 writing to the EFI on the OSX drive; the Win7 installer put the Microsoft EFI on the OSX drive instead of the Windows drive. It didn't affect the booting of either, but it made the Windows drive dependent on presence of the OSX drive. Also the presence of other SATA storage devices caused problems with the installer.

I'd like to try the upgrade without physically removing the NVMe card or disconnecting SATA storage devices, because I would need to unplug all the cables in the back, pull the tower off the desk, unplug the SATA cables, remove the video card blocking the M.2 slot.

So my plan is to:

1. Disable all the unneeded SATA ports in BIOS.
2. Remove NVMe drive from the boot order in BIOS, booting directly off the Win10 drive.
3. Before running the Win10 installer, I'll use device manager to disable the NVMe.

Will this work? Is there something else I can do to make sure Win10 avoids writing to the drive containing OSX/Clover?
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@Project 2501

The safest way to do this is by disconnecting the disk on which macOS resides. If it's SATA, disable that port in BIOS. If it is NVMe, it is better to physically disconnect it from the board.
It is safe to leave disks that do not have an operating system attached.

Also it's a good idea to put Windows disk as first in BIOS while installing.

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1 hour ago, miliuco said:

Also it's a good idea to put Windows disk as first in BIOS while installing.

Windows always bully it's way to be the first Boot Disk in the BIOS until you change the Boot order, that's my experience on my past and present machines.聽:lol:

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Best way is to disable in the BIOS. Most firmwares should be able to do that, even with NVMe. Once it's installed, it should be fine for most updates - I haven't had issues doing updates or upgrading from Windows 10->11 from within the OS.

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2 hours ago, 1Revenger1 said:

Best way is to disable in the BIOS. Most firmwares should be able to do that, even with NVMe. Once it's installed, it should be fine for most updates - I haven't had issues doing updates or upgrading from Windows 10->11 from within the OS.

I tried looking for a way to disable the NVMe slot, but I couldn't find it. Somebody in another thread told me about how to remove the NVMe from the boot list, but I'm not sure if that is the same as disabling it since I can still see it in device manager. I found the method to disable the SATA ports under the I/O section. I'll look again and maybe even RTFM馃槂; perhaps it is buried in a submenu that I missed.

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11 minutes ago, Project 2501 said:

I tried looking for a way to disable the NVMe slot, but I couldn't find it. Somebody in another thread told me about how to remove the NVMe from the boot list, but I'm not sure if that is the same as disabling it since I can still see it in device manager. I found the method to disable the SATA ports under the I/O section. I'll look again and maybe even RTFM馃槂; perhaps it is buried in a submenu that I missed.

My mobo hasn't option to disable NVMe without聽physically disconnecting it.

Removing NVMe disk from boot BIOS options is another thing, the disk remains plugged and visible for windows install program.

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Very useful option, thank goodness present in my bios, but I wonder if one is unable to disable the drives or he doesn't want to take half the case apart , what happens if he installs Windows anyway ... Osx will not start anymore? I think everyone has an emergency usb to boot and restore osx, Efi partitions, in case of overwriting ... or am I wrong?

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What happens depends on how you have your boot loader set up. Windows likes to shove it's EFI files in an already existing EFI partition in my experience. It doesn't wipe EFI partitions I don't think, but will overwrite EFI/BOOT/bootx64.efi. If both OpenCore and Windows are added to your boot entries, then this doesn't really matter? This all depends on windows not wiping the EFI partition though, which I doubt it does?

Worst case scenario is that you backup your EFI somewhere like on to a USB, and replace it if something breaks. There's nothing inherently wrong with two OSes sharing an EFI partition - I have grub and OC on the same partition, with Window's EFI on another.

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19 minutes ago, antuneddu said:

Very useful option, thank goodness present in my bios, but I wonder if one is unable to disable the drives or he doesn't want to take half the case apart , what happens if he installs Windows anyway ... Osx will not start anymore? I think everyone has an emergency usb to boot and restore osx, Efi partitions, in case of overwriting ... or am I wrong?

I still was able to boot both MacOS and Windows when it happened in my old machine. It's just that the Windows disc can't boot on its own since the Microsoft EFI installed on the other disc (it created a subdirectory in EFI... just like CLOVER). If something happened to the MacOS disc, I would not be able to boot Windows as a fall back. I was able to fix it the last time without a complete reinstall (can't remember how); just wanted to avoid the issue in the first place. This is just pure laziness on my part... I'll will remove the NVMe if I have too.

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@antuneddu@1Revenger1@Project 2501

I have had a recent experience with the final version of Windows 11.聽I did not have Windows 10 so I created the install USB from macOS. I didn't unplug the NVMe disk on which macOS resides (I didn't think about it) and installed Windows 11 on the other NVMe disk.


What happened was that Windows 11 setup program did NOT create EFI partition on the Windows disk (just a small initial partition of less than 20 MB called System Reserved that allows Windows to boot directly from BIOS) and put into the EFI partition of the macOS disk the boot loader files (EFI/Microsoft folder with Boot and Recovery folders inside).
In short, Windows 11 put its bootloader in OpenCore's EFI folder without damaging other files but did not create EFI partition on the disk it is installed on.


This has not caused me major problems because Windows boots well by selecting its disk in the BIOS menu and also boots well with a custom entry pointed to the macOS disk (not the Windows one) to the path \EFI\Microsoft\Boot\bootmgfw. efi.
But it is something to keep in mind when installing Windows without unplugging the macOS disk with OpenCore.

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6 minutes ago, Project 2501 said:

I still was able to boot both MacOS and Windows when it happened in my old machine. It's just that the Windows disc can't boot on its own since the Microsoft EFI installed on the other disc (it created a subdirectory in EFI... just like CLOVER). If something happened to the MacOS disc, I would not be able to boot Windows as a fall back. I was able to fix it the last time without a complete reinstall (can't remember how); just wanted to avoid the issue in the first place. This is just pure laziness on my part... I'll will remove the NVMe if I have too.

I've read your post at the same time muy post was uploaded. I see Windows has also put its boot loader in the EFI partition of the macOS disk. Now you're able to boot Windows from the OpenCore picker. What's strange to me is that Windows doesn't boot directly from BIOS.

Run diskutil list from Terminal and see the partitions inside Windows disk. Do you see more than one? names and sizes?

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10 minutes ago, miliuco said:

@antuneddu@1Revenger1@Project 2501

I have had a recent experience with the final version of Windows 11.聽I did not have Windows 10 so I created the install USB from macOS. I didn't unplug the NVMe disk on which macOS resides (I didn't think about it) and installed Windows 11 on the other NVMe disk.


What happened was that Windows 11 setup program did NOT create EFI partition on the Windows disk (just a small initial partition of less than 20 MB called System Reserved that allows Windows to boot directly from BIOS) and put into the EFI partition of the macOS disk the boot loader files (EFI/Microsoft folder with Boot and Recovery folders inside).
In short, Windows 11 put its bootloader in OpenCore's EFI folder without damaging other files but did not create EFI partition on the disk it is installed on.


This has not caused me major problems because Windows boots well by selecting its disk in the BIOS menu and also boots well with a custom entry pointed to the macOS disk (not the Windows one) to the path \EFI\Microsoft\Boot\bootmgfw. efi.
But it is something to keep in mind when installing Windows without unplugging the macOS disk with OpenCore.

Unfortunately, Google translate doesn't help me that much 馃槉, I find it hard to comment, but it seems to me that in the end it is not all this disaster and that the thing is still solvable.

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1 minute ago, antuneddu said:

Unfortunately, Google translate doesn't help me that much 馃槉, I find it hard to comment, but it seems to me that in the end it is not all this disaster and that the thing is still solvable.

I think it's Google translated + my poor English 馃槙

You're right, at least in my case it's not a major problem but I was very surprised when I saw the windows disk without EFI partition.

Ma siamo persone intelligenti che sanno come risolvere i problemi聽馃槀

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1 hour ago, miliuco said:

I've read your post at the same time muy post was uploaded. I see Windows has also put its boot loader in the EFI partition of the macOS disk. Now you're able to boot Windows from the OpenCore picker. What's strange to me is that Windows doesn't boot directly from BIOS.

Run diskutil list from Terminal and see the partitions inside Windows disk. Do you see more than one? names and sizes?

The problem I was referring to was my OLD machine with Yosemite/Win7. I was just hoping to avoid this issue upgrading my CURRENT Mojave/Win10 machine. My Win10 disc has a proper EFI partition with the Microsoft bootloader, because I installed it first without having the NVMe in the M.2 slot, but I have a feeling Win10 upgrade might install the updated EFI to the MacOS disc instead.

Looking back on this thread, I'm a bit embarrassed about how seriously I was taking this. I simply wanted to make sure the Win10 and MacOS will be able to boot independently, but it guess I made is sound like a potential catastrophe. I always have a backup bootloader on a USB flash drive just in case. You'd think Windows would install its EFI on the disc it resides, but that is not the case.

Edit: "...withOUT having the NVMe in the M.2 slot..."

Edited by Project 2501
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Thanks for all your suggestions! Quick followup...

Went ahead and pulled the NVMe and disabled the SATA ports in BIOS. "Upgrade in Place" went without a hitch, as expected. Good news is that it wasn't has hard as I thought it would be. It turns out I misremembered which M.2 slot I used. I used the one near the CPU socket and there was enough聽 clearance with the cooler to remove the NVMe without unplugging anything inside.

Also used the opportunity to clear out all the accumulated dust.

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