If you have your video previews format to cineform or just import plain cineform mov files, Premiere is unable to playback without dropping frames.
You have to change the video previews to DNxHD or I-Frame MPEG to make it smooth again.
This makes rendered timelines to be more laggy than unrendered!
I've seen several threads with bad playback performance that most likely are affected by this.
Has anyone figured out what's wrong with cineform playback?
The problem still exists with 13.0.1. Several frame drops on rendered timeline using cineform 10bit as preview file format.
The timeline is HD with High Quality playback set to off. So there shouldn't be any drop frames at all.
The disk is high performance >600MBps read speed.