The playback becomes choppy after a few seconds of playback. I'm using MP4 from a GoPro. Playback is at 1/2 resolution and have cleaned out media cache database. There aren't real effect and very minor editing so it shouldn't be any memory issue.
I'm on a iMac 2.7ghz i5 with 8GB RAM in OS 10.8
6GB RAM dedicated for PP
Anyone able to help?
Try what is suggested in this help doc: http://helpx.adobe.com/premiere-pro/kb/playback-stops-loops-soundbooth -premiere.html
GoPro material is extremely demanding on the system in CS6. Even on much more powerful systems than yours, a 4 GoPro camera multicam sequence shows choppy behaviour. Your i5 CPU is simply not powerful enough for that material and the amount of memory and disk setup in an iMac do not help either.