How to install windows 8.1 with EFI boot to external hdd on iMac late 2013

Discussion in 'iMac' started by blackwhite999, Dec 10, 2014.

  1. blackwhite999 macrumors member

    blackwhite999

    Joined:
    Apr 2, 2011
    #1
    hi everyone,
    How to install windows 8.1 with EFI boot to external hdd on iMac late 2013?
    I'm playing Fifa 15 on bootcamp. pls help
     
  2. yjchua95, Dec 11, 2014
    Last edited: Dec 14, 2014

    yjchua95 macrumors 604

    Joined:
    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #2
    Just run Boot Camp assistant and that's it.

    Haswell Macs will install Windows in UEFI via Boot Camp Assistant automatically.

    Edit: Saw that it was for external drive.

    I used this guide: http://www.admin-magazine.com/Articles/Putting-Windows-8-on-a-USB-Drive

    But somehow, it won't install in EFI. I formatted my external drive with GUID partition table and FAT32, then used gdisk (command line utility) to remove hybrid MBR so that it would appear as GUID to both OS X and Windows, and still it doesn't install in EFI.
     
  3. espnfanco macrumors newbie

    Joined:
    Dec 9, 2014
    #4
    I'm glad I came across this post. I just bought an external thunderbolt ssd and want to install windows 8.1 on it for gaming. I currently have an iMac 2013 and windows 7 on it partitioned using boot camp. My goal is to delete windows 7 and use the 1tb fusion fully on OS X and install windows 8.1 on the external ssd. Do I have to remove windows 7 first or can bootcamp recognize two windows? I would like to get 8.1 going first before I remove windows 7 if that's possible.
     
  4. yjchua95 macrumors 604

    Joined:
    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #5
    Update:

    I got EFI booting to work on an external Windows to Go drive. You'll need a Windows virtual machine in Parallels/VMware.

    Here are the instructions:
    Connect external drive to Windows VM.

    What you need:
    install.wim file (obtain this from your Windows ISO)

    Open elevated cmd.exe

    Note: All commands aren't case sensitive, including pathway to files.

    Type diskpart
    Type list disk
    Take note of the disk you want to select
    Type select disk 1 (if your disk is Disk 1)
    Type clean
    Type convert gpt
    Type create partition EFI size=100
    Type format quick fs=fat32 label=EFI
    Type assign letter=S
    Type create partition primary
    Type format fs=ntfs quick label=W2G (or any other name you wish for label)
    Type assign letter=E
    Type exit

    Open up File Explorer. In your C drive, create a new folder named WIN2GO.
    Put the install.wim file in this folder

    Back in cmd.exe:
    Type dism /apply-image /imagefile:C:\WIN2GO\install.wim /index:1 /applydir:E:\ (this process will take quite a while)
    Type E:\Windows\System32\bcdboot E:\Windows /s S: /f UEFI

    Restart your entire Mac. After the chime, hold down Option and when prompted to select your boot drive, select EFI Boot.

    Proceed installation normally.

    After installation, install Boot Camp drivers.
     

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