"OK, now you have confused me.  Do I want them equal, or twice?  I have a 4 core system.  Should I set threads to 4, or 8?"

Try a few test scenes at final render settings, and compare render times, using 4 threads, then using 8 threads.

In most scenes, my Core i7 did about the same, whether it was 4 or 8 threads, but on other scenes (which I would guess involved more fetching), 4 threads let cores go idle periodically, whereas rendering with 8 threads kept the cores busy (and thus rendered more quickly).

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5