GUI is as slow as cubase 8?

If I click on a midi region, it would take about 1 second to open the midi editor, and when I draw notes randomly (keep clicking in the midi editor) I can see obvious notes lag/latency, not as smooth as when I use cubase 3…
Anyone meets the same occasion? I’m using a mac pro which I think is powerful enough.

Cubase 3? Wow. I am not a mac user but I have heard there are recent issues with Cubase and Apple. Best of luck to you.