I would check that the wire colors match the pin-out before you connect them up. Figure 1: Pin numbers for an N64 plug (left) and a Gamecube socket (right). Credit to this diagram goes to the Cube64 ...

gc_n64_usb if a firmware for Atmel AVR micro-controllers which allows one to connect an Nintendo 64 or Gamecube controller to a PC with an USB port. The joystick is implemented as a standard HID ...