IBM Personal Computer AT Manual To Operations page 296

2
Did you receive a
1XX
error?
XX:XX:XX
ERROR
SYSTEM UNIT 1XX
END - TEST 100
PRESS ENTER TO CONTINUE
?
(X can be any number.)
YES Note the error and have your system unit
serviced. Be sure your Key Lock key is
with your system unit.
NO You have completed the system unit and
system clock test. Press Enter
(..-J )
and
refer to the screen for the next test.
100-2 Test