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Guide: Multibooting UEFI on Separate Drives

Going Bald

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Apologies (being a nube) do you mean hitting like F12, choose boot option and choose the UEFI OS? I don't see in there where to select the optimum defaults, tks.
No, I mean hit the Delete key at power-on to get into the UEFI/BIOS and reset everything the way you need it to run OS X instead of Windows.
 
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No, I mean hit the Delete key at power-on to get into the UEFI/BIOS and reset everything the way you need it to run OS X instead of Windows.
Got it - I tried that too - I did finally went through the reinstall of the OS again which gets me logged into the OS previously installed (guess it updates some things but keeps my apple account set info and files). I fear doing anything else at this point, I've read to install Clover_v2.3k_r3320-UEFI.pkg or use Clover Configurator so not sure what to do next in order to get a stable Mac system, then worry about why the Windows SSD does not mount. I tried using the install DVD to repair and said that drive was locked?
 
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Got it - I tried that too - I did finally went through the reinstall of the OS again which gets me logged into the OS previously installed (guess it updates some things but keeps my apple account set info and files). I fear doing anything else at this point, I've read to install Clover_v2.3k_r3320-UEFI.pkg or use Clover Configurator so not sure what to do next in order to get a stable Mac system, then worry about why the Windows SSD does not mount. I tried using the install DVD to repair and said that drive was locked?

So Mac now boots consistently using Clover_v2.3k_r3763 and managed to fix some other things via Clover Configurator Version 4.32.1. - however my Windows SSD Boot drive is still not showing up. It's there, I can tell looking at it from Mac Disk Utility it still has files on it - strange the name is now "untitled" as I gave it the name SSD Win. My son set up the Windows originally so not sure where to go from here, hate to wipe out/erase all that hard work - any ideas?

DiskUtilitySSDWin.png
 

Going Bald

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So Mac now boots consistently using Clover_v2.3k_r3763 and managed to fix some other things via Clover Configurator Version 4.32.1. - however my Windows SSD Boot drive is still not showing up. It's there, I can tell looking at it from Mac Disk Utility it still has files on it - strange the name is now "untitled" as I gave it the name SSD Win. My son set up the Windows originally so not sure where to go from here, hate to wipe out/erase all that hard work - any ideas?
I see only one partition - if you remove ALL drives other than the Windows drive, can you boot Windows at all?
If you can, run msinfo32.exe and see if the drive is GPT formatted or MBR formatted. If it is telling you the drive is locked when you use the install media to boot and select Repair, then I suspect what happened is that the Windows EFI partition was created on a different drive from the Windows install drive and you have deleted that partition when you formatted or removed that other drive. If this is the case, re-installation of Windows from scratch is the easiest option unless you are familiar with command line in Windows and want to use Diskpart to fix the drive boot sector.
 
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Is it necessary to use three USBs? Is it possible that some technique (e.g. Yumi) can be used to create one single multi-boot usb disk for the installation? Thanks!
 

Going Bald

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Is it necessary to use three USBs? Is it possible that some technique (e.g. Yumi) can be used to create one single multi-boot usb disk for the installation? Thanks!
No idea, never tried it.
 
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Hello. I read the guide and it was very explaining.
I have 2 SSD and an HDD and I want to make a multiboot using a drive for each system (windows 10, OSX sierra, Linux mint) but the windows 10 are already installed in the first SSD and I cannot perform a clean install at the time. Can I skip the first step of the guide and follow only the next two steps?
 

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Hello. I read the guide and it was very explaining.
I have 2 SSD and an HDD and I want to make a multiboot using a drive for each system (windows 10, OSX sierra, Linux mint) but the windows 10 are already installed in the first SSD and I cannot perform a clean install at the time. Can I skip the first step of the guide and follow only the next two steps?
Is your Windows installed UEFI mode or Legacy Mode? If UEFI, then no problem. If Legacy, Clover UEFI will not boot it. OTOH, you can still use the Fn hot key to select a boot device to boot Windows if you want to leave the existing install alone.
 
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In my C disk, I have an EFI partition around 100 MB. I suppose I am at UEFI mode. correct?
 

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In my C disk, I have an EFI partition around 100 MB. I suppose I am at UEFI mode. correct?
click start, click run, type msinfo32 in the box and hit enter. Look for BIOS mode in the resulting screen.
 
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