IBM RT PC Options Installation page 74

2-30 Options Installation
9. Connect P14 on the power cable to the 4-pin connector on the
rear of the fixed-disk drive in position D. Connect the ground
wire from the power cable to the ground tab on the drive.
Note: Internal fixed-disk drives may differ in appearance.
Data, signal, and power connectors, however, remain in the same
relative positions.
10. Remove the screw holding the drive adapter in adapter slot 1.
Slide the adapter out of the slot, leaving the cables attached.