Dell Latitude LM - Manual (Page 70)

4-14 Dell Latitude LM Reference and Troubleshooting Guide
fault by moving the program to another computer
and running it there.)
• The computer halts in the middle of performing cal-
culations or complex mathematical operations.
Subtests
The subtests that constitute the System Set Test Group and the
computer functions they confirm follow:
• CMOS Confidence Test
Checks the nonvolatile RAM (NVRAM) for accessi-
bility and reliability of data storage by performing a
data pattern check and verifying the uniqueness of
memory addresses.
• DMA Controller Test
Tests the direct memory access (DMA) controller
and verifies the correct operation of its page and
channel registers by writing patterns to the registers.
• Real-Time Clock Test
Confirms the functionality and accuracy of the com-
puter’s real-time clock (RTC).
• System Speaker Test
Checks the functionality of the speaker by generat-
ing eight tones.
• Secondary Cache Test
Confirms the functionality of the secondary
(external) cache on the system board.
• System Timers Test
Checks the timers used by the microprocessor for
event counting, frequency generation, and other
functions. Only the functions that can be activated
by software are tested.
• Interrupt Controller Test
Generates an interrupt on each interrupt request
(IRQ) line to verify that devices using that line can
communicate with the microprocessor and that the
interrupt controller sends the correct memory
addresses to the microprocessor.
• Coprocessor Calculation Test
Checks the use of different types of numbers and the
math coprocessor’s ability to calculate correctly.
• Coprocessor Duty Cycle Test
Tests the math coprocessor’s ability to perform com-
plex mathematical operations.
• Coprocessor Error Exception Test
Verifies the math coprocessor’s ability to handle
errors and to send IRQs to the microprocessor.
• PC Card Controller Test
Checks the functionality of the PC Card controller
on the system board.
• Thermal Control Test
Checks the functionality of the thermal-monitoring
and microprocessor speed-switching device on the
system board. This test does not apply to the Dell
Latitude LM.
V
ideo Test Group
The subtests in the Video Test Group verify the proper
operation of the video controller and the video control
circuitry installed in the computer. These subtests check
for the correct operation of the readable registers in the
video circuitry and the controller. They write, read, and
verify data patterns in the cursor registers of the control-
ler. The Video Test Group also provides additional
subtests to test the color features of the color display or
an external color monitor.
Why Run a Video Test?
Many of the symptoms that would prompt you to run a
subtest in the Video Test Group are obvious, because the
display is the visual component of the computer. Before
you run the Video Test Group or any of its subtests, you
should make sure that the problem is not occurring in the
software or caused by a hardware change.
If the following symptoms still occur, run the appropriate
test(s) as follows:
• If your display or external monitor shows a partially
formed or distorted image, run all of the subtests in the
Video Test Group.
• If the alignment of text or images is off, regardless of
the program you are running, run the Text Mode