IBM F50 RS/6000 7025 - Manual (Page 218)

e. Attach the SSA cables from the SSA adapter to the SSA bulkhead
connectors, as show. Refer to the SSA documentation for information on
connecting these cables.
14. Backplane D installation is complete.
15. If you are installing a backplane E, continue with step 16 on page 5-75,
otherwise continue with step 26 on page 5-80.
5-74 IBM RS/6000 7025 F50 Series User's Guide