From Internet Recovery
Boot to internet recovery (Press CMD option + R) on startup.
Select Utilities at the top
Select Terminal
Now type “sysctl -a | grep machdep.cpu” and press enter, you screen will display lots of information about your MAC CPU
From within MacOS
Press the CMD and space key
Type “Terminal” now press enter/return
Type “sysctl -a | grep machdep.cpu” and press enter, you screen will display lots of information about your MAC CPU