I run a 1.2GHz AMD with 1GB RAM, and P6 isn't slow; as far as dial twisting goes, anyway. There are delays going into the material room, and when switching back to preview after rendering, but it was ever thus. It may be an issue with your video adaptor, since P6 will use that to render the preview. Try switching between OpenGL and SreeD modes to see if there's a difference; and, as always, make sure your drivers are up-to-date.