You can get the box back if you don't render in progressive mode.  However, all cores will be put to work on the same box.  This is to prevent one core from being left along to finish a complex section while the rest of the cores sit idle.  But given that there does not appear to be any change in the quality of the render between the two modes and that with progressive you can spot a flaw early on and cancel and fix rather than wait till the image is 3/4 finished to see the flaw, that should save time.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13