At the moment BIMx global illumination does utilize only one processor core. For us, at the moment, with our recent projects, it takes a little too long a day/night to render.
We have opted out of the GI render for now, and we just turn it off. After that, BIMx creation will take only minutes or so. It doesn't look so good, but we have to present/deliver the model.
btw. Cinerender does utilize cores better. GI is a must there.
AC25, Rhino6/7+Grasshopper, TwinMotion • Mac Pro 6,1 E5-1650v2-3,5GHz/128GB/eGPU:6800XT/11.6.5 • HP Z4/Xeon W-2195/256GB/RX6800XT/W10ProWS