I tested rendered an old model at a very high resolution output. Poser 11 took longer using Dual GPU rendering. (About 14 minutes 50 seconds). If Poser 12 does use dual-card render I can't find the option. But using a single GPU card produced a faster render at around 8 minutes 18 seconds. However the lighting on the skin was different and produced no glossy highlights, in comparison to Poser 11.