For a wiring diagram of an Y-cable with which you can use two joysticks on your Amstrad/Schneider CPC, see [[Joystick Y-cables]].
The CPC+/GX4000 they have two digital joystick ports, which works work same as with the an Y-cable, including for eight Y-cable-style with 8 diodes, and without Fire 3. This is bringing up some possible problems:
* the eight diodes in the direction lines can cause problems with peripherals that use the joystick port as bi-directional I/O port
* the missing diodes in the fire button lines can cause conflicts between player 1 and 2