Joystick Adapter InsideHere are a ton of PC joystick interface circuits “Fake Joystick circuit, the wire between multi-IO card and joystick connector, adding second joystick to PC joystick interface, Y-cable problems with soundcards and how to solve them, soundcard joystick port problem solver, build your own joysticks and controllers , convert Atari-style joystick to PC joystick port, use PC joystick port to measure temperature and light levels, connect other circuits to PC joystick port , using the joystick port as general purpose input .” Link.