I have updated my ssd to a 1tb and partitioned my drive. I have Monterey now on one side but want to have Mojave as well on the other partition. When I down load mojave it says this is too old. How do I target the in stall to the desired partition
MacBook Pro 13″
FYI, it is a terrible idea to partition any drive. People usually discover some time later that one or more of the partitions are too small usually requiring the user to start completely over again.
If you want to divide the drive up into sections and you are using the APFS file system, then just create new APFS volumes within the same Container. These new APFS volumes act a lot like partitions, but don't require physical size limitations since all of the other APFS volumes within the Container share the same storage pool.
Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support
Use more than one version of macOS on Mac - Apple Support
I have done it , as follows
take the ssd out of your Mac ( running Monterey on one side)
now put it in to a ssd external case. Using a Mac running mojarve or older down load superduper and plug it in follow the instructions to make a copy of the old Mac’s drive on to your ssd and make it bootable.
now once done put the ssd in to your mac and turn on hold the alt as soon as you apple logo. Select the partion side you want and your away done
As @a brody has already mentioned, macOS will on boot on hardware that the particular OS is compatible.
If a Mac ships from the factory with macOS 10.15 Catalina, then it cannot run macOS 10.14 Mojave. There is one small exception though. If a Mac model existed prior to the release of lets say Catalina in this example, then that particular model can still run the previous OS Mojave. It only pertains to that one very specific model. If a new model was released at the same time as Catalina (or a model is released after), then the oldest supported version of macOS is Catalina.
A perfect example of this is the MacBook Pro 13" (2019) model which according to MacTracker was released in July 2019 running macOS 10.14.5 (18F2058) Mojave. This model was not discontinued until May 2020. All computers for this model series sold after Catalina was launched in October 2019 would ship with macOS 10.15 Catalina, but a user could downgrade the OS to macOS 10.14.5 (build 18F2058)+ Mojave if they wished.
However, the new (at the time) MacBook Pro 16" (2019) model first released in November 2019 cannot be downgraded to Mojave since this specific model did not exists prior to the launch of Catalina. The lowest version of macOS supported for the MacBook Pro 16" (2019) model is macOS 10.15.1 with build 19B2093.
This has been the way Apple has worked for decades....as far back as I can recall...even to the PPC days and the pre-OSX days.
If your Mac falls into the gray area that I mentioned, then that is why your "trick" works. Once reason installing Mojave directly does not work is if you are using an older version of the Mojave installer that pre-dates the release of your Mac model since all Macs have a specific minimum version of macOS that must be met which includes the minor patch level and even the actual build number of the OS.
Unfortunately you neglected to mention the exact model of your Mac where you say you are using Mojave. You can get the exact model of the Mac by clicking the Apple menu and selecting "About This Mac".
You can only install Mojave on a Mac older than Mojave. Internet recovery for a Mac released during Mojave's release year will also install Mojave on the Mac.
Run two os on a partition drive
