Epson 20 - Manual (Page 141)

If a fault in the main board is found, a number from 101 to 108 and
an error message appear. This message is in the following format:
l0x-System board error
where x is a number from 1 to 8 that represents the specific LSI circuit
in which the error is found. Your service dealer needs this information
to find and correct the problem.
If an I/O ROM checksum error occurs, you see this message:
xxxx0 ROM error
where xxxx is the number of the segment of the bad I/O ROM.
Clock and CMOS RAM Check
When the system device check is completed successfully, the computer
checks the timer and CMOS RAM. If the information contained in
the RAM does not match the actual system installation, you see one
of these messages:
161-System options not set
(Run SETUP in DIAGNOSTICS)
162-System options not set
(Run SETUP in DIAGNOSTICS)
The information stored in the CMOS RAM must be corrected. Run
the Setup program provided on the Reference diskette to correct the
installation information.
If
the system clock has not been set, you see this message:
163-Timer & Date not set
(Run SETUP in DIAGNOSTICS)
If the memory allocation has not been set, you see this message:
lb&Memory size error
(Run SETUP in DIAGNOSTICS)
B-2 Power-on Diagnostics