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I have an early 2013 Retina MacBook Pro with only a Windows 10 partition. MacOS is not currently installed on the machine. The Windows 10 partition is encrypted with BitLocker and because of the partitions layout, I believe MacOS cannot currently be installed alongside Windows.

Can I temporarily swap the original SSD for a new empty compatible SATA III and perform a clean install of MacOS on the new SDD? I would like to see if any EFI and SMC updates are available for the MacBook.

When I'm done with MacOS, I would like to put the original SDD back in and continue where I left off Windows 10.

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  • Before this question can be answered, One would need to know if Windows is BIOS or EFI booting. The reason for asking is that firmware updates require a FAT32 formatted EFI partition on the primary internal drive.
    – David Anderson
    Commented Jan 12, 2018 at 1:15
  • @DavidAnderson, That's a good comment. The SSD uses MBR, which in my understanding means Windows is BIOS booting. There is not much of a BIOS screen when the computer is turned on, just the plain white background. Does that change your answer below?
    – u17
    Commented Jan 12, 2018 at 12:05
  • The SSD uses MBR now because when it used to use GPT, the Bootcamp Assistant complained “Windows cannot be installed on to this disk. The selected disk is of the GPT partition style.”
    – u17
    Commented Jan 12, 2018 at 12:14
  • From a Windows Command Prompt, run diskmgmt.msc and see if your Disk 0 has an "EFI System Partition". If so, then you are probably are using a EFI boot method. Otherwise, you are using the BIOS boot method. Did you use the Boot Camp Assistant to install Windows 10? Or, did you first install an older version of Windows and then upgrade to Windows 10?
    – David Anderson
    Commented Jan 12, 2018 at 12:26
  • Both the EFI and BIOS boot methods require a MBR. The EFI boot method also requires a GPT. The BIOS boot method can also use a GPT, but a GPT is not always required.Your Mac can boot Windows 10 using either method, but the preferred method for Windows 10 is EFI.
    – David Anderson
    Commented Jan 12, 2018 at 12:38

2 Answers 2

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The boot volume does not need to be internal for OS X. Use any USB drive, boot while holding cmd+R. You will boot the recovery partition (from the disk of existing or other online, so it might ask you for a network connection). Then just install on the external drive and boot from that by holding alt/option during startup.

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  • I like this approach. I am a bit worried though that the MacOS installer could corrupt the Windows partitions because it does not understand them when the original SSD is not taken out. This happened when I tried to set-up Bootcamp with BitLocker along MacOS.
    – u17
    Commented Jan 11, 2018 at 18:52
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    You could just unplug the SSD if you want to be 100% safe on that and plug it back in later.
    – Kevin Grabher
    Commented Jan 11, 2018 at 18:58
  • If you unplug the SSD, then the firmware updates can not be installed.
    – David Anderson
    Commented Jan 12, 2018 at 1:17
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What to propose should work. You will need to boot to internet macOS Recovery to install macOS. See the Apple website: How to reinstall macOS. When booted to macOS Recovery, you will probably have to use the Disk Utility to initialize, before installing macOS. If this does not install High Sierra, then you will need to download and install High Sierra from the Apps Store. This is the easiest way to get the latest firmware Updates.

When changing drives, you may need to hold down the option key at startup to invoke the Startup Manager. To make a desired operation system the default, hold down the control before selecting the arrow.

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