Epson EL 3S/33 - Manual (Page 49)

Before you install SIMMs, check the following guidelines to
ensure that they will work properly:
Use only 30-pin, fast-page mode SIMMs that operate at an
access speed of 70ns (nanoseconds) or faster. Be sure all the
SIMMs operate at the same speed.
Use the correct SIMM configuration to add the amount of
memory you want. See the table above.
Inserting SIMMs
Follow these steps to install SIMMs:
1. Refer to the illustration on page 3-5 to locate the SIMM
sockets near the front of the computer.
2. Remove any option cards that may be blocking your access
to the SIMM sockets. (See page 3-16 for instructions.)
3-10 Installing and Removing Options