IBM RT PC Options Installation page 65

10. Look at the diagram of the cable bundle.
Warning: The jumpers on the adapter must be reset if
the adapter was previously installed in adapter slot 2. See
"IBM Personal Computer AT Fixed-Disk and Diskette Drive
Adapter" on page 2-53 if the new drive is an R40 fixed-disk
drive, or "IBM RT PC ESDI Magnetic Media Adapter" on page
2-54 if the new drive is an R70 fixed-disk drive, for jumper
settings.
Using the drive adapter previously removed from drive position
E, connect C-AB and C-CD to the 34-pin connectors on the
adapter.
Section 2. Removing and Installing Drives in IBM 6150 2-21