External drive boot loop (EFI) and non-bootable (WinPE)

Hi guys,

I have some issues with installing my bootcamp installation on an external drive. Can you guys please help me out; I have search all around the internet and I have tried numerous of things.

Finally, I decided to buy WinClone as an ultimate way to succeed; so far nothing so I hope I didn’t waste my money.

My setup:

  • Mac OS X (11.0.1) Big Sur
  • MacBook Pro (13-inch, 2020)
  • Thunderbolt 3 eGPU / SSD enclosure (HP Omen)
  • Win10_20H2_v2_Dutch_x64.iso (yes, Im dutch).

What I want to achieve:

  • Run Windows from the thunderbolt 3 enclosure, eventually leverage from the eGPU so I can fully use windows (too…)

What I did so far:

  • Set T2 boot options to allow external devices
  • Install drivers with /recurse (mentioned on this forum and 9to5 Mac)
  • I successfully installed Bootcamp Windows on the internal harddrive. It works and have installed everything I needed (also for the enclosure whatever is needed).
  • I successfully made a image of the ‘internal’ bootcamp with WinClone
  • I successfully restored that image to the external drive (I can see it from Mac OS)
  • I set the boot mode of the restored drive to legacy, winPE and EFI
  • Flashed another external drive with Bootcamp (same issues, infinite bootloop)
  • Injected drivers via WinClone

What I got so far:

  • With legacy bootable - nothing happens
  • With EFI bootable - It goes into a boot loop with the windows / apple logo.
  • With WinPE bootable - I directly go into windows boot manager where it states that ‘a required device isn’t connected or can’t be accessed

Any help? Thanks!

The issue is most likely the thunderbolt driver as a mass storage device for external booting. Windows needs that driver to be able to boot. There is also some items in the registry that need to be switched sometimes when migrating to an external drive:

Hi thanks for the link, I remember that one from a long while ago and I directly applied the registry fix. Before making the bootcamp image I did the cleanup with Sysprep.

Unfortunately, I didn’t succeed. When I applied this to the Thunderbolt drive I simply got a black screen, nothing happend.

Also on a simply Sandisk SSD drive (which I installed bootcamp on earlier) I was not able to make it work again. It went into a bootloop again. I suspect it has something to do with the usb / thunderbolt controller in the MacBook Pro 2020, I was not able to make the thunderbolt work on the internal bootcamp drive too.