This must be done more than 30 times every second to provide a responsive game input . The actual acquisition frequency and value usually depend on the joystick 's resistance inside , noise , CPU speed and the total joystick-capacitor 's RC time constant . The typical implementation of a game port uses a capacitor and a simple voltage comparator , which together form a sort of crude ramp-compare ADC , which needs to be periodically polled and reset at precise moments to read an input , something that must be done several times ( generally above 30 ) per second to provide a responsive game input , and the actual acquisition frequency and value typically depend on the joystick 's internal resistance , noise , CPU speed and the total joystick-capacitor 's RC time constant .