Downgrade from Catalina on new iMac

[rfattaleh]

We are looking to upgrade our server machine and have found the (almost) best option for us to be a new 2019 27" iMac.

This machine has Catalina loaded onto it, but that model originally had Mojave (10.14.4) pre installed.

For this machine to host our application to some of our older machines in the office (some as old as 2009), we would need to downgrade to High Sierra.

Unfortunately, the information I could find stated that while it was possible (though not easy) to downgrade back to Mojave (10.14.4), there was no information of being able to go down to High Sierra. I am sure the process is involved, but we are just looking to know if it is possible on these new machines before we purchase.

Has anyone had success in downgrading to High Sierra on 2019 iMacs? or have any information as to how/if we can do such a thing?

 

[ThunderSkunk]

It won’t work... The old OS doesn‘t have the hardware drivers for the new imac, because that new hardware didn’t exist when the OS was being written. So the OS is just smart enough to check first, and won’t install.

The 2019 iMac is the bees knees, but the previous model is right up there in performance too. Plus, you’ll get TB2 ports, so you can use all the mindisplayport things like cinema displays and whatnot, with the benefit of that gear having matured and become inexpensive now.

 

[chrfr]

We are looking to upgrade our server machine and have found the (almost) best option for us to be a new 2019 27" iMac.

This machine has Catalina loaded onto it, but that model originally had Mojave (10.14.4) pre installed.

For this machine to host our application to some of our older machines in the office (some as old as 2009), we would need to downgrade to High Sierra.

Apple doesn't sell any computers today which will run High Sierra, aside from the iMac Pro, so this is not an option. What application is it you're trying to use?

 

[mj_]

The last iMac to support High Sierra was the 2017 iMac (which has two Thunderbolt 3 ports by the way, the last one with Thunderbolt 2 was the 2015 iMac). The 2019 will only support as far back as Mojave.

 

[gilby101]

We are looking to upgrade our server machine and have found the (almost) best option for us to be a new 2019 27" iMac.

A 'server' machine with a 27" screen! Surely a Mac Mini would be better as a server.

For this machine to host our application to some of our older machines in the office (some as old as 2009), we would need to downgrade to High Sierra.

Why does age of client require the 'server' to run High Sierra?

If you really need HS, I suggest a Late 2014 or Late 2012 Mac Mini. Or, if your server needs a 27" screen, a 2017 iMac.