Epson Progression U12 - Manual (Page 81)

Although your computer can use any SIMM that complies
with industry standards, it is best to use Epson SIMM
option kits to ensure reliability and compatibility. If you
choose another type of SIMM kit, check the shape of the
SIMM to make sure it will fit in your computer. (Some
manufacturers’ SIMMs are longer on one side, which
prevents them from fitting inside the socket correctly.)
There are two SIMM sockets on the main system board, and
each can contain one memory module. You can install SIMMs
with a capacity of 1MB, 4MB, 16MB or 64MB.
The following table shows the possible SIMM configurations;
do not install memory in any other configuration. Remember
that there is
already 4MB of memory soldered onto the main
system board.
SIMM configuration
16MB 1MB 21MB
1MB 16MB 21MB
3-12 Installing and Removing Options