What is the oldest version of Mac OS that can be used on retina displays?

Question

For development (backward testing with older OS versions) I need to install older mac OS versions. Ideally I'd want to go as far back as Snow Leopard.

I have an iMac with retina (model iMac15,1). Before I hunt and dig around for old installation media and experiment, I'd like to find out what is the oldest version that properly supports retina displays (i.e. allows for a properly readable screen)?

The web says Retina was introduced with Macbook Pro 2012 which would be around Mountain Lion.

Expierences (first hand) anyone?

Answer 1

Patrix above is right. Trying to install versions that were released prior to the hardware is the way straight into driver hell (you may or may not be able to copy some driver files from newer OS to older, which may work or not but we'll leave such stunts to Windows folks).

Since your necessity for backward OS seems to be temporary (for testing), I'd recommend to use a virtual machine. Desktop, VMWare Fusion, and VirtualBox should be viable solutions (as recommended here by someone answering a similar question on the apple discussion forum). I've tried in the past (with other machines, pre retina) and it was a frustrating experience.

It remains to be seen how this affects retina vs. non retina though (I have no first hand experience with virtual machines and how they map retina screens to the guest OS).

Answer 2

The limitiation isn't so much the display as the hardware overall. You can't install OS versions older than the hardware because older versions don't bring all the required drivers etc. for various components.

Your iMac (late 2014) came with OSX 10.10 pre-installed, so this is as far as you can go back.