Standard Drive Base speed

I noticed that the standard drive base is much faster if I am using the built-in programs compared to use my own program. With the built-in program max speed ist about 120 rpm (getting data by implemented data display when pushing the down-button twice). With RobotC I am not able to have a speed higher then 100 rpm (writing the motor speed into a variable and displaying it on the brain).
Is there any possibility to speed-up the motor to 120 rpm with my own program?
Many thanks for your hints!