You can get utilities which will defragment RAM, and when I was using P5 in a half-gig of RAM that could free up quite a big chunk of available RAM. There's something about Poser which doesn't work well with virtual memory. With a full gigabyte, I've been able to render quite large images with reasonable speed, images comparable to what my film scanner will produce. P6 seems to handle some of the process a little faster, but has introduced a few new weirdnesses. So, right now, I'm wondering if P6 was worth getting. But I'm just at the awkward point: it has a lot of little changes that will trip up a P5 user, and I'm trying to get used to them. But I don't think the rendering engine is improved at a fundamental level. There are extra shader nodes, but...