I have been using an Apple Cinema Display since I bought it new in 2010. It’s currently attached to a 2018 MacBook Pro running Mojave.
The MBP would often beachball when I had too many Safari tabs open. When I ran Activity Monitor, I saw kernel_task and WindowServer using a lot of system resources.
Last night I remembered reading an article that said WindowServer can slow your system down if you’re running an external display. And I thought, “I don’t think I have this problem when the MBP is running disconnected.”
So I disconnected the Cinema Display and all morning the MBP has been zooming along.
Could the Cinema Display indeed be the cause of the problem or is my newly speeded up Mac a coincidence? And is there a fix other than buying a new display?
I have the MBP connected to the Cinema Display using this USB-C to Mini Display Port adapter. Maybe the adapter is the problem? https://amzn.to/2JVE6eb
P.S. I’m actually not particularly dissatisfied just working in the 13" MBP display with no external monitor attached.