Has anyone downgraded an iMac 5 (Retina 5k, 27-inch, Late 2014) pre-installed with Yosemite to an older version of Mac OS?

My Pro Tools 10 does´t work with Yosemite. I have two days to resolve this, if not I have to return the computer.

I have tried it to downgrade and it appears this symbol:


If somebody has done the downgrade, please give a step-by-step solution.


It is impossible to downgrade this Mac to anything less than Yosemite - the hardware forbids it. You have proved this in practice by getting the No Boot sign.

As for Pro Tools: from the Avid site: Note: Pro Tools 10.x and earlier (including Pro Tools Express) will not be tested/qualified with Yosemite (or Mavericks).

You will have to upgrade your Pro Tools to version 11 if you want to use Yosemite.

  • Or even version 12 as that is out
    – mmmmmm
    Mar 25 '15 at 22:19

Software can be downgraded only as far as the drivers will go. As the iMac 5k Retina has a rather fancy graphics card that likely didn't exist when they wrote Mavericks, it is highly unlikely you will get anything older to work on it.

So, here's what you do:

  • Reinstall Yosemite using the Recovery Partition (or Internet recovery if you already broke the recovery partition)

One of:

  • Upgrade Pro Tools to a Yosemite compatible version

  • Get VMware Fusion and run Mavericks (and Pro Tools) in a virtual machine. Once you have started on this route you can also run pretty much any x86-compatible operating system all the way back to DOS 6. You will probably want more memory.

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