thank you for your reply,
I managed to optimize my scene thanks to SI_Samples, but I still do not understand why my processor does not work 100% even if I try to put a high priority.

hello I want to simulate cloth of 7 HD character for a student production. but it is really very slow. I have a 3.5GHz 2700k, 16gb ram and a GTX680. when I look in the task manager, my CPU uses 8 theard but they never exceed 50%.Is It Normal? Syflex it is the best solution ?, or is there any other s...