Yun He wrote: > As subject, how much difference does the FAST or SLOW refinement level effect > the final models in MD? Does it really worth for a loooong computation to > build a more accurate model?

They change the amount of simulated annealing done (number of steps at each temperature, and number of temperatures to use). It's probably only worth using slower refinement levels when you have larger models, but you should try them and see for yourself.

Ben Webb, Modeller Caretaker