iMac Pro iMac Pro won't do external boot camp drive

Discussion in 'iMac' started by Hmizer, Feb 13, 2018.

  1. Hmizer macrumors newbie

    Hmizer

    Joined:
    Feb 13, 2018
    Location:
    Midwest
    #1
    So I've created an EFI, w2g, w10pro SSD (Samsung T5) which boots just fine from my Windows machines and my 2015 MBP13r.

    My new iMac Pro sees the drive at boot but fails to boot with a bless error.

    Ironic that the first Mac with a high end GPU cannot boot from a Windows to Go drive.

    Any ideas? Created the drive with a Parallels 13, W10 VM using WinToUSB free.
     
  2. eddjedi macrumors 6502

    Joined:
    Sep 7, 2011
    #2
    I always found Windows To Go very hit and miss with Macs, I have been trying to reliably use it ever since Microsoft came up with the idea but in reality I've found over half of the Macs I've tried it on won't boot it from USB sticks. I ended up using VMs instead as I don't fancy committing some of my internal storage to Bootcamp.
     
  3. Hmizer thread starter macrumors newbie

    Hmizer

    Joined:
    Feb 13, 2018
    Location:
    Midwest
    #3
    Well the whole point is W10 gaming with the Vega GPU so VM won't do.
     
  4. sputnikBA macrumors 6502

    Joined:
    Jan 2, 2018
    #4
    (I’m sure you already did) but have you changed your secure boot settings to allow booting from another drive?
     
  5. nambuccaheadsau macrumors 65816

    nambuccaheadsau

    Joined:
    Oct 19, 2007
    Location:
    Nambucca Heads Australia
    #5
    Nothing to do with your iMac Pro just Windows does not like booting from an external as this is an anti-piracy measure by Microsoft. No inferences!

    There are work round just Google it Having said that your immediate problem may be with APFS and the format structure of the external drive.
     
  6. jerwin macrumors 68020

    Joined:
    Jun 13, 2015
    #6
    I went the dism /apply-image route. when I wanted to install windows to a external SSD.

    And I boot with the option key...
     
  7. Hmizer thread starter macrumors newbie

    Hmizer

    Joined:
    Feb 13, 2018
    Location:
    Midwest
    #7
    You did read that my 2015, 13", MacBook Pro Retina will boot to this drive with no issues, right?
    Ergo, not windows.
    --- Post Merged, Feb 13, 2018 ---
    If you do this from the security settings in the bootloader (control-R during boot) you get the same error:
    "The bless tool was unable to set the current boot disk"

    or something like that.

    Again, this drive boots flawlessly on my MacBook Pro (2015) running High Sierra.
     
  8. sputnikBA macrumors 6502

    Joined:
    Jan 2, 2018
    #8
    The MBP doesnt have the T2 chip / new secure-boot process though. So thats the first thing that came to mind.

    I wasn't aware you could disable or change the boot settings at start up - thought it was a thing you had to first boot into OS X to change in there (for obvious security reasons). But I don't have an iMP myself to try it so I'm sure you are right.
     
  9. SaSaSushi macrumors 68040

    SaSaSushi

    Joined:
    Aug 8, 2007
    Location:
    Takamatsu, Japan
    #9
    Not having an iMac Pro either, I don't know if this will work but it's worth a try:

    Download the trial version of Winclone and then select the Windows installation and from the Tools menu choose Make EFI Bootable.

    That worked for me after I resized my Bootcamp partition on a Thunderbolt external drive and it stopped booting with the "bless tool" errors. YMMV

    Winclone is well worth the purchase by the way. It's a really helpful app.
     
  10. Hmizer thread starter macrumors newbie

    Hmizer

    Joined:
    Feb 13, 2018
    Location:
    Midwest
    #10
    I'm a twit. I enabled booting from an external drive, but on the iMac Pro you also have to enable booting from an unsigned operating system. Now it works! It's insecure as anyone could boot to anything, but my internal SSD is encrypted so I think it's going to work for me.
     
  11. kellywilkins89 macrumors newbie

    kellywilkins89

    Joined:
    Jun 19, 2018
    Location:
    Orem, UT
    #11
    Thank you for sharing this! Saved my skin!
     

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