Triple boot OSX, Windows 8.1 and 10

Discussion in 'Windows, Linux & Others on the Mac' started by Yannicks, May 7, 2015.

  1. Yannicks macrumors newbie

    May 7, 2015
    I've been working on windows using bootcamp for quite a while now and want to test Windows 10. I've tried to find ways to install a second Windows install but I couldn't find confirmation that it is possible.

    Could I just create and extra FAT partition, reboot and install windows 10 on it?
  2. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    On Macs that support UEFI booting of Windows (Haswell and later Macs), you can do so. This is because since Windows is installed as UEFI, OS X no longer uses a hybrid MBR partition. It uses GPT entirely and hence more than 4 partitions can be present.

    On pre-Haswell Macs, there could only be an OS X partition and a single BIOS-CSM Windows partition (Windows cannot be installed as UEFI in such Macs), and since Windows had to be installed as BIOS-CSM on such Macs, OS X has to format the drive as hybrid MBR (where OS X sees the drive as GPT and Windows sees the drive as MBR). There are actually 4 partitions in this manner - OS X itself already takes up 3 partitions (OS X itself, Recovery and EFI, of which the last two are hidden), plus Windows. So in this way, 4 partitions are present and that is the maximum partition limit in hybrid MBR drives.
  3. Yannicks thread starter macrumors newbie

    May 7, 2015
    Cool, I'll go ahead then and see how it goes (have a late 2014 MBP).
    Do I need any special bootloader or will the default one work just fine? Does it matter what partitioning program I use the prepare my partitions? Is there an extra step I need to take to create a shared windows data/documents drive?

    I can hardly believe it would be this easy as I can find 0 tutorials about this scenario online.
  4. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    For partitioning, just use Boot Camp Assistant or Disk Utility.

    The default boot loader will do. I have Windows 8.1 and Windows 10 (TP) on my late-2013 15" rMBP alongside OS X and it's all good.
  5. ActionableMango macrumors G3


    Sep 21, 2010
    I currently triple boot OS X, Windows 7, and Windows 8.1 EFI on an old Nehalem Mac Pro, which is very much pre-Haswell.
  6. Yannicks, May 13, 2015
    Last edited: May 13, 2015

    Yannicks thread starter macrumors newbie

    May 7, 2015
    Ok, so it didn't work.

    I tried partitioning with Disk utility but it just hang preparing the resize of the osx partition for hours.

    So next I tried with Gparted created following partitions: OSX, NTFS (for windows 10), Fat32 (as a shared files drive), BOOTCAMP (windows8.1 was created earlier) and 2 small partitions DiskOs3 and DiskOs5.

    Rebooted but then only the OSX partition is working. The windows 8.1 partition stopped working with a "Your PC needs to be repaired" 0x000000e and can't be repaired with the windows CD repair option nor with FixMbr.

    The newly created NTFS disk can't be used to install windows 10 either because i'm getting the following error:
    "Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks.
    Windows cannot be installed to this hard disk space. The selected disk has the maximum number of partitions of this type."

    So what did I do wrong... how to fix this mess?
  7. Yannicks thread starter macrumors newbie

    May 7, 2015
  8. z31fanatic macrumors 6502a


    Mar 7, 2015
    Mukilteo, WA USA
    I am afraid you'll have to start from the beginning. Wipe the whole drive, make 3 partitions with all three being GPT. One for MacOS obviously, and two Fat32 for the two Windows installs.
    I haven't tried it but in theory it should work.
  9. Yannicks thread starter macrumors newbie

    May 7, 2015
    I ran into this program called Easy Recovery Essentials and got my old windows 8 install working again. Unfortunately now my windows 10 EFI bootrecord is broken by the tool. But this same tool can also fix the windows 10 install again... breaking the windows 8 install again. :)

    So would be lovely if an EFI expert could guide me how to get both working without needing this bootdisk tool everytime I want to switch.
  10. lowendlinux Contributor


    Sep 24, 2014
    North Country (way upstate NY)

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