IBM RT PC Options Installation page 92

6. Pull the wire latch aside, place the diskette drive on the rails, and slide it
into drive position B. Ensure that the wire latches hold the drive firmly
in place.
7. Look at the diagram of the disk and diskette cable bundle, which is
already installed. The first two (if two are installed) fixed-disk drives
and the diskette drive in position A connect to this cable bundle.
To Fixed-Disk Drives
In Positions C and D
To Drive Adapter
In Slot 1 "';::::~_-.1110..-&
Section 2. Removing and Installing Drives in IBM 6150 2-51