Dr. MOS is, in short, a technology where a pair of mosfets (high & low) and a mosfet driver are integrated into one circuit. Instead of three (driver, mosfet low, mosfet up) you have one. They have nothing to do with phase count, but MSI says they run cooler and output less ripple. MSI is not the only company that uses integrated mosfets; Gigabyte has them too, for example on GA770T-UD3P.