power mac g5 cpu question

I have a G5 2.3 x 2. This weekend I have been using Mpeg Streamclip to edit some video files. Just for fun I checked the stats using istat pro. Mpeg Streamclip was only using 15-20 % cpu. The computer was as high as 86% idle. What up with that? Is there a way to assign more power? I need more power I mean I don't want 86 % idle, can I give 86 % to the task?

Thanks for the help