Dell XPS 8940 Service Manual page 56

Steps
1. Slide the back I/O-ports on the system board into the front I/O-slots on the chassis and align the screw holes on the system board
with the screw holes on the chassis.
2. Replace the screw (#6-32x3.8) that secures the system board to the chassis.
3. Install the voltage regulator heat
NOTE: The voltage regulator heat sink is shipped as a separate unit and it does not ship along with the system board.
If reusing the voltage regulator heat sink, remove it from the old system board and transfer it to the new system
board.
4. Replace the eight screws (#6-32) that secure the system board to the chassis.
5. Route and connect all the cables that you disconnected from the system board.
56 Removing and installing components
sink.