Apple Mac Performa 640 series - Manual (Page 152)

Installing a SIMM
1 Remove the SIMM from its static-proof bag.
Handle the SIMM by its edges. Avoid touching the connectors.
2 Insert the SIMM into the SIMM slot on the DOS-compatibility card assembly, as shown
in the illustration. (Your SIMM may have components on one or both sides, as shown.)
The SIMM fits into the slot only one way.
Make sure the notch on the SIMM is on this side. Insert the SIMM into the SIMM slot.
(Insert the SIMM at a slight angle.)
Connectors
SIMM slot Vertical plate
144 Appendix B