If you were at 83% on 5 cores, then it's not hyperthreading. So I'd use 6.

The first step was to get using 100% CPU. That's out of the way. So now we could look at render settings and materials.

Yes Poser is not the fastest by far. But there are quite a few things that increase the render time non-linearly. I never use the automated slider. I select settings myself. Also, when IDL is involved, I don't even use Poser's advanced render settings dialog. It's still to simplified. I use the add-on one included with it, found in menu Scripts/Partners/Dimension3D/Render Firefly.

There is also the question of final render versus test render. Among test renders there are lighting tests versus material tests. For lighting tests, I really jack up speed in exchange for quality. There was a thread when Poser 8 came out where a challenge was thrown down - to make a good render in less than 8 minutes with IDL. I did it easily.

Have a look:

Breathtaking indirect lighting renders in under 8 minutes?

 

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)