I don't render much in Poser these days (modo does a better job) but when I do I'm always amazed that any buckets are getting rendered at all because my CPU is at idle (or very, very little usage) throughout the process. So if the CPU isn't processing the buckets, who is? The little elves? It's a quad core Q6600 running in XP SP2, Poser7. There was a thread about this a while back but there wasn't a clear answer to the question of why the CPU isn't at 100% usage during a render.

Modo is no fun to watch because the completed bucket action zips around the screen so fast it's hard to follow it.  ;-)