IBM RT PC Options Installation page 205

2. Install each module with the notch facing the bottom edge of the
card, as shown in the following drawing:
3. Align the pins of each module with the connector on the card and
press each of the 16 modules in place.
Go to "IBM PC Graphics Memory Expansion Card" on page 7-10 to
install the expansion card.
Warning: You must install this adapter in adapter slot 3 or 6 in
IBM 6150 and in slot 1 in IBM 6151.
Installing: See the system unit diagram for the correct adapter
slot.
Section 7. Display Adapter Options 7-13