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Mojave and Catalina on the same iMac

How is it done? Is there things to be done to write over Mojave? I' looking for hints. I know it can be done—just looking for some guidance. I' am doing it to maintain usage of my 32 bit apps.

iMac Pro

Posted on Jan 24, 2022 3:20 PM

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Question marked as Top-ranking reply

Posted on Jan 25, 2022 1:10 AM

Hi Donald


I know nothing about Catalina for like you I want to retain the use of 32 bit apps so stayed with Mojave.


I have Mojave and High Sierra on a single SSD formatted as APFS and each OS is installed on different volumes. I can choose to boot in either but not possible to boot both at same time if that is what you are hoping for.


Assuming your iMac Pro is capable of running Catalina you can probably install Catalina on a separate volume, container or a second hard drive.


You could boot in either MacOS and perhaps share some files but in Catalina you would not be able to run 32 bit apps which are on the Mojave volume.


So I think the answer to your question is ‘yes’ but you’d only be able to boot from one OS at a time.


I shall be interested to read other responses.

2 replies
Question marked as Top-ranking reply

Jan 25, 2022 1:10 AM in response to Donald Holevoet

Hi Donald


I know nothing about Catalina for like you I want to retain the use of 32 bit apps so stayed with Mojave.


I have Mojave and High Sierra on a single SSD formatted as APFS and each OS is installed on different volumes. I can choose to boot in either but not possible to boot both at same time if that is what you are hoping for.


Assuming your iMac Pro is capable of running Catalina you can probably install Catalina on a separate volume, container or a second hard drive.


You could boot in either MacOS and perhaps share some files but in Catalina you would not be able to run 32 bit apps which are on the Mojave volume.


So I think the answer to your question is ‘yes’ but you’d only be able to boot from one OS at a time.


I shall be interested to read other responses.

Jan 25, 2022 8:47 AM in response to Need_help_give_help

Thank you for your response. I am not trying to run both at the same time—I know that is impossible. Catalina will do what I need, and yes, it will run on my iMac Pro. Unlike the Mac Pro that I had here, I cannot swop out hard drives and install Catalina on a separate volume. I will need to purchase a separate drive, install Catalina, and pick which system to fun from at boot. Apple is pushing Monterey to update my Mojave, so I know Catalina will work, but it is all those 32 bit apps I don't want to lose.

Yesterday, I read an old post from 2020 where somebody made it sound like they had both system on the same volume—Mojave and Catalina. I don't know that is possible, writing one system over another, and keeping both intact. Your response makes it clear a second drive is needed. Thanks.

Mojave and Catalina on the same iMac

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