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Guide: Multibooting UEFI on Separate Drives

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If I am understanding you correctly, you want to have Mojave on a new drive you installed and you want to then install Win10 on the existing drive with Mojave on it.

Clone Samsung 970 to other drive.
Disconnect Mac OS drive or disable SATA port in UEFI/BIOS.
Boot Windows 10 install media. At the screen which asks you to select a drive/partition to install on, select each partition and click delete until

hit shift+F10 to open a command prompt.
type the following lines, hitting enter at end of each line
diskpart
list disk

//determine which drive is the one you want if more than one drive is connected. Be very careful here as you will destroy all data on the drive you select, especially if you use clean all which zeros the drive. Do not use clean all very often on a SSD as it shortens the life of the SSD. You will be able to tell the USB by the smaller size//
say your drive is disk 0, type

select disk 0
clean
exit
exit

this leaves your drive with all unallocated space. Select this unallocated space to install Win10 and hit continue/install button. Win10 installer will take it from there.
not exactly, I want to keep mojave in my samsung 970 pro "it is already installed and working perfectly", I have another Samsung ssd drive that is where I want to install windows, thank you very much for your help and answer
 
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If Clover will boot it, or if you are using the Fxx key to select the Win drive to boot, do not bother.
Earlier Clover versions often had problems with an EFI partition that is not the first partition on the drive. Win 10 install puts WinRe Tools on the first partition, then the EFI partition, but will leave an existing EFI partition as first if it already exists and use it - hence the instruction to create the EFI partition using the Mac Disk Utility. For those who are handy with Windows command line, an elevated prompt at the Win10 install screen and using diskpart to format the drive and create the EFI partition would work as well, but for most, the Mac OS disk utility route is easiest.
Thanks. I think the Clover version on my USB stick is approx 1 year old and it boots Windows fine from existing NVME so I won't have to wipe and re-do.
 
Joined
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Another potentially dumb question but why not just only connect the drive you want to install the OS to and then disconnect drive and do next and so on. Then plug all 3 in and select the MacOS drive as the boot drive so Clover is the bootloader and does the job? Is there something missing here? I would assume this would also help with the issue of Windows getting over-excited and over-writing the EFI priorities and removing Clover (which happens all the time on my dual boot system without some interventions!).
 

Going Bald

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Another potentially dumb question but why not just only connect the drive you want to install the OS to and then disconnect drive and do next and so on. Then plug all 3 in and select the MacOS drive as the boot drive so Clover is the bootloader and does the job? Is there something missing here? I would assume this would also help with the issue of Windows getting over-excited and over-writing the EFI priorities and removing Clover (which happens all the time on my dual boot system without some interventions!).
Precisely why I recommend having only target drive connected - either disconnect or disable ports for other drives in UEFI/BIOS for installation and reconnect/re-enable when installations are finished. This prevents all kinds of hassle between OS's for resources.
 
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