Big Sur 11.2.2 and 32 bit startup disk using 10.14.4

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Level 1

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Big Sur 11.2.2 and 32 bit startup disk using 10.14.4

I have an alternate startup disk on my main drive to run 10.14.4 in order to run 32 bit compatible applications/games. Before upgrading to Big Sur this worked fine. Using the Startup Disk control panel I could switch back and forth without trouble. This time after booting into 32 bit the old OS reports an incompatible disk error, namely the Big Sur partition, and the Big Sur partition is no longer selectable in the old Startup Disk control panel. Thus it is not possible to reboot back into Big Sur using the control panel.

There is a workaround by holding down option during a restart which allows me to select a startup partition and this works, thankfully. However this seems to be a shaky workaround, and I would get locked out if this stopped working. Of course, anyone who did this and didn't know this trick would be immediately locked out of the Big Sur partition which could be disastrous.

So how safe is it for me to continue to use this workaround, and can this be fixed to make the old OS recognize the Big Sur partition transparently?

iMac 27″, macOS 10.12

Posted on Mar 10, 2021 8:50 PM

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Answer 1

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Lanny

Level 6

13,207 points

Mar 10, 2021 9:15 PM in response to naiman

What you describe as a "workaround," is actually the preferred method for using 2 different OS versions. The older 32 bit version OS's System Preferences can not be expected to be compatible with the newer 64 bit OS version. However, Big Sur's startup system preferences will most likely be able to recognize the 32 bit OS version.

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Answer 2

naiman Author

Level 1

6 points

Mar 10, 2021 9:40 PM in response to Lanny

Thanks that answers my question - this trick will continue to work. I was concerned that if the old OS took over the booting process that it could get stuck in the old OS. Evidently the new OS is smart enough to load first and then check before handing off to the old OS even if the old OS partition is labeled as the startup drive.

On the other hand at some future date Apple may decide not to support dual booting into the 32 bit OS and one could get stuck without being able to switch back. This would be very bad. Hopefully that day is far off.

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Big Sur 11.2.2 and 32 bit startup disk using 10.14.4

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