I already posted on a 3d dedicated forum and with a help of a user (ran a scene on his workstation) I managed to reduce the probable culprit to hardware settings. Low poly, optimized scenes are going hundreds of times too slow with the CPU barely doing any job (it is not mistakenly setup for GPU) while the messy, 50mil poly scenes are going as planned with CPU usage on the limit. It's highly unlikely it is software (checked two different renders, the only improbability would be some general Max settings but I ran through them) and so it seems like the undemanding hole which doesn't seem to use CPU power at all is caused by some hardware setup. The hardware is a 12 core Xeon X5650 on a Dell motherboard/workstation with 24GB RAM. Ideas?
Thanks in advance.
Thanks in advance.