IBM Personal Computer XT Manual To Operations page 71

Diagnostic Testing
During the diagnostic tests that follow, you will need a
scratch diskette. If you do not have a scratch diskette,
go to "Diskette Format Procedure" on page Start 40-1.
During the diagnostic tests, you may be asked to record
an error message. This information is needed when you
have your system serviced.
Following are examples of error messages you may
receive. A message ending in 00 means the test finished
successfully.
In the examples, X can be any character.
Example 1
XX:XX:XX
ERROR· SYSTEM UNIT XXXX
Example 2
XX:XX:XX
ERROR· EXPANSION UNIT XXXX
The unit in which your options are installed determines
if the error message reads SYSTEM UNIT or
EXPANSION UNIT
April 1984
Test 000-1