Control of D0 Installation Guide
XIR Kit v2.2/1.2:
You will have to solder a wire from the XIR board to the XBOX Motherboard.
Solder one end of the wire to the hole in the middle top of the XIR, labeled 'D0'.
The other end of the wire you must solder to D0 on the xbox motherboard.
For full compatibility, the XIR must be the only unit connected to D0 (this means if the modchip is connected to D0, it must be disconnected).
For exact information on D0 locations you can visit Xbox-Scene.com