IBM 3270 Hardware User's Manual page 78

If You
Add:
384KB*
Set the Switches
By Installing These
on the Cards to:
Memory Cards: 12345678
128KB Memory-Printer Adapter 1001
+
256KB Expansion Card
128KB Memory-Printer Adapter
0101
+
64/256KB Option with 256KB
installed 10010001
64/256KB Option with 256KB 10110001
installed
+
64/256KB Option with 128KB 01110100
installed
*If you have an expansion unit, remember to reset the switches on the
extender card in the system unit to match the new total memory. The
new total = the amount of memory you are adding + 256KB. See the
section on the expansion unit for the correct switch settings.
Now, go to the Option Instruction booklets, and
follow the instructions there.
Chapter 2. Setting Up and Checking Your 3270 PC 2-61