Oracle X5-4 Service Manual page 229

13. Remove the four screws securing the backplane bus bar to the motherboard.
The backplane board rests on the two support flanges.
Disconnect the two power supply cables from the back of the power supply
14.
backplane board.
15. Loosen the green captive screw that secures the motherboard to the chassis.
Replace the Power Supply Backplane Board (FRU)
Servicing FRU Components 229