There are certain applications I use that required me to boot in 32-bit mode in OS X 10.7 (Lion). I could do this by holding down the "2" and "3" keys upon startup. This no longer works since I have upgraded to OS X 10.8.

Is there still a way I can force Mountain Lion to boot in 32-bit mode?

  • I admit to being curious about this. 32-bit applications can still run in a 64-bit kernel, for sure? At least they can under Lion. (But they will need 32-bit library code to link to, and perhaps ML does not provide that.) Commented Jul 29, 2012 at 16:19
  • @HaraldHanche-Olsen This is the case for most software, but applications like Pro Tools that relies on hardware(specificly the MBox bundle), this becomes more problematic. The hardware glitches can be quite bad. Commented Dec 3, 2012 at 16:53

3 Answers 3


As you have a definitive no - here is a workaround that most people are pursuing in this case. Run Lion in a virtualized environment on top of Mountain Lion. The commercial products like VMware Fusion, Parallels and VirtualBox all might assist you until those applications can be updated or replaced.

Of course, you could dual boot most hardware but a virtual solution might work longer term if you choose to upgrade hardware.

  • Thanks! Yes, it appears I'll have to use a workaround.
    – skc
    Commented Jul 29, 2012 at 15:54


Mountain Lion only boots using a 64-bit kernel which does not support loading 32-bit kernel extensions.

via Arstechnica


I found on MacRumors a solution to this but I don't know the exact commands add it. The user said 'Just add arch=i386 in to boot.plist and reboot.'

I'm also trying to find a solution and do not want to run a VM for this purpose. Cisco VPN won't run in 64 bit and only runs in 32 bit OS X.

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