I am currently running a 2017 iMac (High Sierra 10.13.6). I have a 2008 Mac Pro (El Capitan 10.11.6) with some old software I'd like to continuing using. Can I remove the startup disk from the 2008 Mac Pro and connect it to my iMac and run the old software? Would I need to boot the iMac from the Mac Pro startup disk for it work? Is it safe to do that?
iMac Line (2012 and Later)
You cannot boot from any OS version older than what your Mac came with. So you cannot boot from your old disk at all. You may be able to access it and get some files, but apps may or may not launch or run or they may just crash.
1. It depends on the software. Applications which can be drag-installed or are from the Mac App Store are more likely to work than ones which have dedicated installers or installation packages.
2. You can't.
3. It doesn't matter.
(181727)
Unless you are transferring everything over, malware is not going to "crawl" over by itself. I would not transfer a lot of very old things - some apps may no longer run/be compatible with the newer OS, so I would not bother. You can just move over files, pics, etc. (things you created).
Thank you Niel. Toward the end of using the 2008 Mac Pro, I was seeing problems with the startup disk steadily losing space. Possibly Time Machine was backing up copies? I was never able to chase the problem down and there seemed to be some other odd bugs as well (sorry I can't be more specific, it's been a while now). If I start using that old startup disk as an external drive with the new iMac do I run any risk of these problems transferring to the iMac?
Thank you Babowa
If I hook up the old disk as an external drive on the iMac, is it possible for malware or other problems to migrate to the iMac?
You can use Target Disk Mode to transfer files, like applications, from Mac to another.
Transfer files between two Mac computers using target disk mode - Apple Support
You can connect your Mac Pro to your iMac using a Thunderbolt 3 to Thunderbolt 2 adapter and a Thunderbolt 2 to FireWire 800 adapter. You can't connect two Macs with Target Disk Mode using USB or Ethernet.
Old Software on a Newish iMac
