The real life EFIS knobs on the 777, 747, 737 and 736 are actually a turn-and-hold spring loaded type with about 45 degrees of motion in either direction possible before it hits the stops. Deflecting the knob more results in faster acceleration of the value being entered on the PFD. They are not free rotating knobs like they are in the NGX, which actually models them incorrectly.
To enable correct operation of virtual hardware in conjunction with the 777, 747, 737 and 736: In the FMC, select MENU > PMDG SETUP > OPTIONS > SIMULATION > Page 3, MINIMUMS & BARO KNOBS and set it to the rotary option.