Epson 3865X Plus User Manual page 132

Looking at the SIMM sockets vertically, the sockets are
labeled as shown below.
1L 2L 3L 4L 5L 6L 1H 2H 3H 4H 5H 6H
3. If an option card is blocking access to the SIMM sockets,
follow the steps in "Removing an Option Card," on page
5-16, to remove the card(s).
5-26 Installing and Removing Options