Install Mojave on another drive

[MoerBoer]

I finally sourced a RX 570 and I can now upgrade to Mojave.

I would prefer doing a clean install on another drive on my cMP 5.1, and keeping my existing High Sierra drive as is.
Is this possible now that I don't have my stock HD 5870 in anymore?

 

[DeltaMac]

Of course.
Boot to Mojave installer.
Run "Reinstall macOS", choosing your other drive as the destination. Could be internal on a different slot in your cMP, or external. This will be best, I think, on a blank partition, or an erased drive, whatever you have. That gives you an absolutely clean install. Then, if you like, when it begins a new-user setup on that drive, you will have the choice of migrating from another drive. You can then migrate from your High Sierra drive, leaving your High Sierra drive untouched, and your new system with everything from the High Sierra system drive, upgraded to use with Mojave. Or, just ignore the migration screen, if you want a simple/clean install of Mojave.
BTW, the Mojave install will automatically change your blank partition to APFS. There's no need to reformat that yourself, the Mojave installer will take care of that for you. It will not change the format of other partitions on that same drive (if you have other partitions on that other drive )

 

[MoerBoer]

Thanks so much for the detailed response DeltaMac!

Much appreciated.

 

[MarkC426]

You can easily install Mojave onto another drive, but it depends what firmware version you are on, as to the gpu you need in?

Read the first few pages here:

https://forums.macrumors.com/threads/mp5-1-what-you-have-to-do-to-upgrade-to-mojave.2142418/

 

[MoerBoer]

Great, thanks so much! You guys are amazing.

 

[FazzMac]

Of course.
Boot to Mojave installer.
Run "Reinstall macOS", choosing your other drive as the destination. Could be internal on a different slot in your cMP, or external. This will be best, I think, on a blank partition, or an erased drive, whatever you have. That gives you an absolutely clean install. Then, if you like, when it begins a new-user setup on that drive, you will have the choice of migrating from another drive. You can then migrate from your High Sierra drive, leaving your High Sierra drive untouched, and your new system with everything from the High Sierra system drive, upgraded to use with Mojave. Or, just ignore the migration screen, if you want a simple/clean install of Mojave.
BTW, the Mojave install will automatically change your blank partition to APFS. There's no need to reformat that yourself, the Mojave installer will take care of that for you. It will not change the format of other partitions on that same drive (if you have other partitions on that other drive )

Where can I find my Mojave Installer? I have a 2018 machine that came with Mojave already installed, where is the installer tucked away at for me to install on an external hard drive?

Thanks!

 

[MarkC426]

You need to download it from the app store.

 

[FazzMac]

You need to download it from the app store.

Ok! Thank you!