Hi crytojoe. I have only recently built a machine that uses a dual-core processor. When I do a render in the render room(top of screen, righthand filmstrip logo button) I see the output of all my cores during a render as a series of sequential "tiles". Each core handles a different tile, and if I recall correctly the tiles are numbered to show which core is rendering which tile. It seems that the preview render does not make use of more than I core. If I am wrong I am sure someone will correct me. Cheers, Dan