Adobe Premiere CS6 has laggy preview with high disk access but low memory use I have a video project including 40 clips, in average 2/3 minutes, at high quality (400MB /min).

If I import a single clip in the project, the video preview is fine, however, having many of them lined after each others eventually causes the video preview to lag. If I pause and give it a few seconds, the preview after resume is fine for a while then starts lagging again.

CPU usage is bellow 20%, RAM is 1.5GB used out of 6.5GB, however disk usage is high. I assume the software can't keep up loading the video fast enough due to the heavy weight.

Is there a way to fix this issue ?
I am working in Adobe Premiere CC 2018, but if memory serves you should be able to still do this in your CS6 version. 

Set an out point 'O' at the end of the clips you want to preview. 
Go up to 'Sequence' in the upper left - and select 'Render In to Out' 

Once they're rendered on your timeline they should play with no lag.