Guide: Multibooting UEFI on Separate Drives

aristeidk · Mar 28, 2020

In the past i was problems with this. With rufus is better but i dont remember the settings.

trs96 · Mar 28, 2020

aristeidk said:
In the past i was problems with this.

It's always worked for me with no problems. Give it another try.

Going Bald · Mar 28, 2020

See https://support.microsoft.com/en-us/help/15088/windows-10-create-installation-media
Select Windows 10, then follow the prompts.

jefftr66 · Mar 30, 2020

Going Bald said:
Did you do this?
For Win10:
Connect a drive, insert OS X Install USB, boot the system and at the POST hit the Function hotkey that allows you to select a boot device. 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.
Remove the OS X Install USB and insert the Win10 USB, boot the system and at the POST hit the Function hotkey that allows you to select a boot device.

Alternatively, you can hit shift+F10 at the first installation screen and use diskpart to clean the drive, convert GPT and create a partition name EFI format FS=FAT32 size 200MB (or larger) before you exit dsikpart and then run the installer. If an EFI partition is already present the installer uses it rather than creating another one.

Clover wants the EFI partition to be the first partition on the drive, not buried behind the recovery/reserved partitions as the independent Windows installer installs it if allowed to create it automatically.

So I already have a working Hack running Catalina on 1 SSD. Do I have to boot into an OX Install USB or can I format the SSD I want to instal Win 10 on with Disk Utility from my Mac desktop? (Basically skip most of the first paragraph and just install from Win10 USB I have)

jefftr66 · Mar 31, 2020

jefftr66 said:
So I already have a working Hack running Catalina on 1 SSD. Do I have to boot into an OX Install USB or can I format the SSD I want to instal Win 10 on with Disk Utility from my Mac desktop? (Basically skip most of the first paragraph and just install from Win10 USB I have)

OK - got it to install but issue with graphics drivers on Win side....

Going Bald · Mar 31, 2020

jefftr66 said:
OK - got it to install but issue with graphics drivers on Win side....

Did you install the drivers for the GPU provided by AMD? If so, did you check for updates?

jefftr66 · Mar 31, 2020

Going Bald said:
Did you install the drivers for the GPU provided by AMD? If so, did you check for updates?

Yup - got a code 43 error which apparently can meet a few things? I started a new thread, thanks.

t33j4y · Mar 31, 2020

I am stuck trying to install Windows 10 Pro on separate SSD.

I have individual control over power to each disk, so I am trying to end with a setup where I power off the OS disk I do not want to boot from and power on the one I want to boot from. That way, I don't have to mess around with Clover or risk corrupting anything on either drive because the OS tries to "fix" stuff.

My system is as described in the profile info - I have Catalina up and running so I know that the HW works

I have followed this from post #1:

For Win10:
Connect a drive, insert OS X Install USB, boot the system and at the POST hit the Function hotkey that allows you to select a boot device. 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.
Remove the OS X Install USB and insert the Win10 USB, boot the system and at the POST hit the Function hotkey that allows you to select a boot device.
Windows shows up as USB: Win10Installer (or whatever you named the USB) and as UEFI USB: Win10Installer.
Select the UEFI USB: Win10Installer and boot the system.
At the installation screen, select Custom Install. At the next screen select the OS X partition and delete it - do not delete the EFI partition. With the resulting free space hi-lited, install Windows to the space. The installer will create and format the partitions for you. When finished, update and install your 3rd party apps and security suite. Reboot to BIOS/UEFI and disable CSM. Save&exit, continue boot to desktop. Shut down, disconnect the drive.

I have
- physically disconnected the SSD with Catalina on it
- physically connected the SSD (a 500GB Barracuda to SATA port 1 - it is the ONLY drive attached
- created the Windows install USB using the Media creation tool - from a PC running Windows 10
- reformatted the Barracuda using Disk Utility (from my Catalina build) to GUID/Mac OS Extended (Journaled) and can confirm that when it shows up in the partition overview in the Windows installer, it HAS an EFI partition.
- ensured that the Windows install USB does boot from UEFI by manually selecting the boot menu (F12) and choosing UEFI Boot: USB
- tried with both Legacy mode (AKA CSM) enabled and disabled
- tried from both a USB 2.0 and 3.0 port (though the USB drive is 3.0)

No matter what I do, I end up with the dreaded "Windows could not prepare the computer to boot into the next phase of installation. To install Windows, restart the installation." message. The installer actually does create the partitions as it should but is unable to copy files and then ends with that message.

I really can't spot what I am doing wrong?

Edit: Hmm.. this seems to suggest that the drive needs to be connected to first SATA port (SATA-0)- I have it on second. I guess I could change that to test. If it works, I can just move it to SATA-1 afterwards, I assume?

jefftr66 · Mar 31, 2020

So you can get to the Windows Install screen? (I just did this last night - almost exact same procedure)

If so I did this additionally