Epson EQUITY 3865X/20 PLUS - Manual (Page 144)

You may also want to test a newly-installed option. Some
options come with their own diagnostics test programs, and you
can test others with the diagnostics programs on your Reference
diskette. You can use the System diagnostics program on your
Reference diskette to test the following:
System memory
Math coprocessor
Serial and parallel ports
Disk drives
Monitors and display adapters
Dot-matrix printers.
See Appendix C for instructions.
6-24 Installing
and Removing Options