I dont know exactly what it does but i think i can explain why i was having the problem i was having. I was using cnc all day today and yesterday and the motors never got more than warm. Before this if i ran any sort of a long programme the motors where getting hot. This might explain why when i tried to go faster the motors overheated and then stalled causing the big steps in the cut i was getting ? So whatever the special mode does the drivers and motors dont like it, or they should be set as certain way. I might email Sorotec and see can they offer any information.