IBM 5155 Manual To Operations page 307

Switch Settings
The positions of these eight switches indicate: if your
system has the Math Coprocessor; the amount of
memory on the system board; the type of display you
are using; and the number of diskette drives installed.
See the figure below.
1 2 3 4 5 6 7 8
~~DDDDDDD
Switch Function
1 Normal operation; always off.
2 Math Coprocessor.
3-4 Amount of system board memory.
5-6 Type of display you are using.
7-8 Number of diskette drives installed.
Switch
Settings
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