If i am not mistaken it is something about how the game was coded that makes it work worse, like graphic card doesn't work like it is suppose to.
Full speed at all times maybe if you have a C2D 8*00's overclocked to 4.0Ghz and a 4850, 4870, GTX260, GTX280 with DX10 or if pcsx2 and/or GSdx can overcome this problem with the code, must be very difficult to make emulator work with so many differents types of codding so just use Software mode for now and be happy that we have software if not it would be 17-22fps walking, use hacks and advance options 45-55fps most of the times for me with the exceptions of special effects that make fps come to 15fps some times.
Are you talking about SW rend. threads? if you are, maybe, it suppose to use 3 cores of your cpu and the other core for the rest of pcsx2, if it is optimized enough it will be faster than using only 1 core, try using the latest Gsdx available but i really can tell by experience since i have C2D, C2Q will lose most of the times against C2D of the same speed but maybe if Software mode is well coded and using the latest windows 7 that is suppose to be more 4 core friendly will make it worth wild having a C2Q even without using video and graphic programs.