After installing the new driver version (456.38), bitcrack gives an error (Error: too many resources requested for launch).
The problem is solved by rolling back to the previous version, but the question arises about the new 30XX line of nVidia.
Did you try to adjust the -b -t -p sizes?
What speeds do you get with older driver?
At my requests 91-92 Mkey / s, after installing a new driver and reducing the -t parameter to 384, the speed dropped to 56 Mkey / s.