Cubase 6 never lets me get over 40% CPU usage before it starts crapping out on me. Even with the buffer size set at maximum!

I'm running a 3.06ghz first gen i7 quad.
Actually... I've never really put much consideration into it, but...
Is anyone able to get around a solid 80% CPU usage out of Cubase before things get 'poppin 'nd click'n?
Is there anyway I can improve CPU usage in Cubase?