CPU not properly rendering in PP

[KR_king]

I noticed this before but never this much.I'm making a quick time laps but I noticed that the playback was extremely laggy even on 1/4 quality. I tried to render it and I saw that Premiere wasn't even using 20% of my cpu!
It's an i7 2600, mercury playback engine with a GTX285, 8GB 1600Mhz and 840/EVO RAID0.

 

Anybody any idea what could cause this problem?

 

 

EDIT: cpu temps are in the low 50, so it's not throttling .

[Levent]

are you using CS6?

just realized you are using cs6 and by the looks of it its related to engine and cuda acceleration issues on old cards take a look at this

Edited April 10, 2014 by Levent

[Nineshadow]

Are you using GPU-accelerated rendering?(CUDA)

[KR_king]

are you using CS6?

just realized you are using cs6 and by the looks of it its related to engine and cuda acceleration issues on old cards take a look at this

 

The strange thing is that I've always used CUDA but when I was rendering or exporting it used my cpu and memory much more, it basically maxed it out and now It doesn't even care. 

 

Are you using GPU-accelerated rendering?(CUDA)

Yes

I've always used it like that, and it worked perfectly. I am running a secondary gpu, maybe it's running on that one? It's an old 8500GT so it would run pretty slow.