The r_finish setting toggles synchronizing every frames.
/seta r_finish 1
Values: “0” or “1”
r_finish is an OpenGL function which ensuring proper timing between various rendering functions and actual frame data output. By setting it to “1” you should experience some ‘jerks’ or ‘stutters’ while moving or looking around.
It is equivalent with the “Sync Every Frame” setting in the game options menu.