Can I run two (2) versions of Mac OS?

[OLDTMR]

I have a Mac 27" Retina (2017) with 64 GB Memory and I'm running Mojave because I need to run photoshop CS6 and I refuse to go the subscription route. Little by little, I'm seeing some drawbacks, mostly it seems with Safari and Apple Mail. I'm a retired designer and I don't need Photoshop every day. So what I was wondering was could I somehow run some kind of dual boot setup where I can update to the latest version of Mac OS for my everyday browsing and mail use, and then have a way to call up my old version of Mojave so I can use Photoshop? Do I need to add an external drive where the new or old OS works from? My Mac has the original internal 250GB SSD root drive, and I have an external 2TB USB Fantom drive where I store everything. The SSD has about 90GB free, is that enough to fit an additional version of OS or do I need to get an external SSD? Is there a way to mirror my current drive on to a 1TB internal drive without any hiccups? Any help on how to do this... if its even possible... would be appreciated. TIA-Mike

 

[rm5]

Hi! Yes, you can dual-boot a newer version of macOS. However, if I were you, I would do it on an entirely new external SSD. You'll need to download the newer version of macOS - I'd go for at least macOS Ventura or newer. There is an Apple Support article all about downloading macOS, so you can follow that. Then, run the installer and select your external SSD as a source for the installation. Hope this helps!