Guide: Multibooting UEFI on Separate Drives

Going Bald said:

Wrong procedure for cleaning a drive for Win10 installation.
Create the Win10 installation USB with the Windows Media creation tool -
see https://www.windowscentral.com/how-create-windows-10-usb-bootable-media-uefi-support

boot the installation tool, hold shift+f10 to get a command window, use diskpart to clean, convert GPT the drive. Exit diskpart. Exit the command window. Select the clean drive to install Win10.

BTW I HIGHLY recommend you disconnect ALL other drives when cleaning drive/installing Win10 on UEFI builds.

Click to expand...

Now I'm a little bit confused. You wrote:
Connect a drive, insert OS X Install USB, boot the system ... Select the OS X Install USB. At the installation screen, select Utilities->Disk Utility and format the drive single partition GUID/Mac OS Extended (Journaled). When done, exit Disk Utility. Quit the OS X installer. That's how I did it ;-)

With the connected drive it's my mistake of course...

** Update **

@Going Bald
My hopefully correct way:

1. Created Win10 USB with Win Media Creation Tool
2. Disconnected OS Sierra Drive
3. Booted from Win10 USB
4. Diskpart, clean Win Drive, convert in GPT, exit
5. Booted from Win10 USB and installed.
6. Bios changed CSM off
7. Clover shows 4 Boot icons for Win and 2 for OS Sierra (HD and Recovery):
Win = Boot Windows from Legacy HD1, Boot Windows from EFI, Boot Windows from Legacy HD4, Boot Microsoft EFI Boot from EFI (from this Win10 starts correctly)
Why it shows 4 Windows Boot icons? How can I hide the 3 icons oder turn it off = Legacy?

Thanks

@Going Bald

I am happy about an answer. Thanks

Three possibly dumb questions, if y'all don't mind putting up with me:

A) Is it guaranteed that having multiple drives plugged in will screw w/ Windows 10 install? My board has one of the M.2 on the rear where it's inaccessible, and I'm not sure yet if I can disable the M.2 slots in the UEFI.

B) Does it still apply that it doesn't matter what order you install the OSes in?

C) If you're running off multiple drives, do you even need Clover, technically, rather than just choosing boot device in the UEFI?

Thanks

N-Bomb said:

Three possibly dumb questions, if y'all don't mind putting up with me:

A) Is it guaranteed that having multiple drives plugged in will screw w/ Windows 10 install? My board has one of the M.2 on the rear where it's inaccessible, and I'm not sure yet if I can disable the M.2 slots in the UEFI.

B) Does it still apply that it doesn't matter what order you install the OSes in?

C) If you're running off multiple drives, do you even need Clover, technically, rather than just choosing boot device in the UEFI?

Thanks

Click to expand...

Win10 installer is usually the guilty party to screwing up other OS drives. If you are reasonably careful in selecting your other OS drives for formatting by their installers, then the Win10 drive should stay OK.

Installing on separate drives the order of installation makes absolutely no difference.

Yes, you need Clover, if only to boot Mac OS. If you want to select boot device from UEFI each time make one of the other OS drives your default boot drive

I have an existing PC with Windows already installed on an M.2 SSD. I want to add another M.2 SSD for High Sierra. Will I need to reformat the Windows SSD and reinstall it first or can I just add the new SSD and do High Sierra install?

chmmr said:

I have an existing PC with Windows already installed on an M.2 SSD. I want to add another M.2 SSD for High Sierra. Will I need to reformat the Windows SSD and reinstall it first or can I just add the new SSD and do High Sierra install?

Click to expand...

Run msinfo32.exe. - this will tell you if you installed legacy BIOS mode or UEFI mode. If legacy, install Clover legacy also.
Otherwise, just format and install on the new M.2 drive, making sure you select the new drive for formatting and not your Windows drive. Best to remove Windows drive. If not possible without disassembling system to get to it, disable the drive in the UEFI temporarily while you install Mac OS, then re-enable.

Going Bald said:

Run msinfo32.exe. - this will tell you if you installed legacy BIOS mode or UEFI mode. If legacy, install Clover legacy also.
Otherwise, just format and install on the new M.2 drive, making sure you select the new drive for formatting and not your Windows drive. Best to remove Windows drive. If not possible without disassembling system to get to it, disable the drive in the UEFI temporarily while you install Mac OS, then re-enable.

Click to expand...

Thanks. I just did this (removed Windows SSD, installed High Sierra, replaced Windows SSD). Windows was installed UEFI and so is High Sierra. Dual-boot is working but only using BIOS F8 menu. Choosing the Windows drive from Clover menu just gives me a black screen with a cursor in the corner. I'm okay with this but fixing Clover boot would be nicer.

@chmmr
Did you do all steps in the guide pinned to the start of this forum regarding installing UEFI on separate drives?

please delete

Going Bald said:

@chmmr
Did you do all steps in the guide pinned to the start of this forum regarding installing UEFI on separate drives?

Click to expand...

The one thing I didn't do is to make an EFI parition using the OSX Installer before installing Windows 10. I installed Windows 10 before I was considering hackintosh, so I just installed it normally.

So if I understand how this all works correctly, this means Win10 created its own EFI partition which cannot be used by Clover to boot that drive?

If this is the case, is it possible I can fix this EFI partition somehow to make it readable by Clover without having to reinstall Windows?