Commodore Amiga has 2 joystick ports where (most of the time) in port 1, a mouse is connected. Since the pinout of these ports are Atari like, Commodore reused the 4 direction pins to send the mouse quadrature signals for both axis. The firmware interprets these quadrature signals and send them via USB as a standard HID mouse. Windows 8 / MAC OS X with an Amiga mouse!? Why not?
More info on how the firmware reads the two rotary encoders here.
Controller pinout
| Pin | FUNCTION | |||||
|---|---|---|---|---|---|---|
| 1 | V-PULSE | |||||
| 2 | H-PULSE | |||||
| 3 | VQ-PULSE | |||||
| 4 | HQ-PULSE | |||||
| 5 | BUTTON 3 (M) | |||||
| 6 | BUTTON 1 (L) | |||||
| 7 | +5V | |||||
| 8 | GND | |||||
| 9 | BUTTON 2 (R) |