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8.2.1
Turn-On Self Teats
The operating system ROM provides self tests that run automatically whenever the computer is turned
on with the operating system ROM installed. However, these self tests do not display any messages
unless an error occurs. In this case an appropriate error message is displayed at the bottom of the
copyright window. The following self tests are executed at turn on:
• The ROil Check-Sum Te.t.
The operating system ROM has a check sum stored in its last four
bytes. This test adds all of the bytes
in
the ROM (except
f~r
the last four bytes) and compares the
sum with the check sum.
• Option.' ROM Ch ... ·Sum
Test. This test checks to see if an optional ROM
PCA
is present. If one
is
found, a check-sum test is performed.
• RAil Te.t.
This test checks the internal RAM and any external RAM modules found.
The self .tests simply indicate that a problem
exists.
To diagnose the problem further, use the service
ROM and the service diagnostic disc as described in section 8.5.
8.2.2 Service ROM Diagnostic Tests
The service ROM contains most of the diagnostic tests that you will need to troubleshoot the
computer .
...... Service ROil ....... nce Test.
When you turn on the computer with the service ROM installed,
the service ROM
sequence test
runs automatically. The sequence test includes all of the following tests:
• Internal RAM Te.t.
This test checks all RAM locations for address and data uniqueness.
If
an inter-
nal RAM error occurs, an error message will identify the RAM Ie to replace (refer to section 8.2.4),
the sequence test will stop, and no more tests can be run.
• IIIIU ,.. ... This test checks all functions of the
MMU (memory management unit).
If an
MMU
error occurs, the error message
is
displayed, the sequence test will stop, and no more tests can be
run.
• Short Ke,b_reI Te.t.
This
test checks to see if a keyboard is plugged into one of the keyboard
jacks and, if so, tests the keyboard.
If
no keyboard
is
connected
to
either jack, an error message
is
displayed.
• DI.pl.r/GPU
Te.t. This
test checks the display RAM and GPU, then presents a series of test pat-
terns. These test patterns can be
used
to spot display faults.
• Flopp,
Disc
T ••
t.
This test checks the operation of the floppy disc drive. You must install a blank,
formatted disc in the drive before this test is
run.
If you do not, an error message will be displayed.
Note that any data or programs on this disc will be lost.
• RTe T .... This test checks
the real-time clock.
• Ixternal
RAil T ....
This test searches for an external RAM module, then checks the operation of
the module and, indirectly, the I/O port
in
which it is installed. The test reports the number of 1<-
bytes of RAM contained in the module, then runs a module diagnostic test and reports whether the
module passed or failed the test.
In testing the computer, this test
is
used to check the data and address lines of each I/O port. The
test is run with a known-good RAM module installed first in port A, then in port
a,
before the
power is turned on.
Always turn off the power before installing or removing a module in an I/O port.
If
an error message occurs, it indicates a failure of the I/O bus or a portion of the logic circuitry since
the RAM module is known to be good.
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