It will all depend on your motherboard on UD5/7 I can run 2133CL7 at 1.7, 2200 CL8 at 1.7; on M4E I need 1.72Vdimm... on the other Asus boards I own Hypers just don't work properly over 1866 divider... ( I can run them 1866CL6 at 1.65Vdimm all day, for 2133Mhz CL8 it's not even stable at 1.76Vdimm)

Purely bios related...