List of Apple computers compatible with macOS Big Sur. MacBook (2015 and later) MacBook Air (2013 and later) MacBook Pro (2013 and later) Mac mini (2014 and later) iMac models (2014 and later) iMac Pro (2017 and later) Mac Pro (2013 and later).
Hello MacPro early 2008 here, running Mac OS X Lion, Mavericks, Yosemite, El Capitan too.
All versions of OS X on this machine run quick and smooth, so no problems here.
El Capitan is the last version of OS X that is compatible with the old slugger.
So we need to find out what might be causing the slow performance on your Mac Pro.
You can download this, https://etrecheck.com/ run the app and copy and paste the results here.
Things that might be impeding your macs performance are lack of hard drive space, lack of RAM, although you seem fine at 12GBs, anti virus software, cleaning or optimisation software, incompatible apps, adware/malware, too many apps opening at login/startup. If you post the results of the etrecheck report we can have look and give you some pointers.
Apr 3, 2017 11:48 PM