OS 10.9 or 10.10

[sfphoto]

Can one install either 10.9 or 10.10 on an external drive partition OR does a previous operating system need to be present on such.
If the latter what OS needs to be present?

The machine is a 2012 Mini with 10.11 - am having issues and want to try an older OS.

Thanks in advance.

 

[treekram]

If you can get the install app for the OS you're interested in, you should be able to use the createinstallmedia command to make a bootable install USB flashdrive of an older OS than is running on the computer. createinstallmedia works as far back as Mavericks.
https://support.apple.com/en-us/HT201372

You should be able to target an external drive partition - you should format it before doing the installation.

I had problems with all Yosemite updates after 10.10.2 on my 2.6Ghz quad-core 2012 Mini. I had regular kernel panics having to do with the GPU. I did not have problems before 10.10.3 and have not had any kernel panics after upgrading to El Capitan. This problem does not seem to be widespread but there were other people who seemed to have the same problem. I did not have any kernel extensions (except maybe for updaters). Maybe it was Adobe Flash but the kernel panic logs didn't indicate that that was the problem.

 

[sfphoto]

If you can get the install app for the OS you're interested in, you should be able to use the createinstallmedia command to make a bootable install USB flashdrive of an older OS than is running on the computer. createinstallmedia works as far back as Mavericks.
https://support.apple.com/en-us/HT201372

You should be able to target an external drive partition - you should format it before doing the installation.

Thank you,

I found fleaBay sellers offering 10.9 and 10.10 either via download or media.