HP Insight Diagnostics - Manual (Page 33)

Troubleshooting 33
Troubleshooting
Troubleshooting memory
The memory test component can perform the following tests:
• Address test—This test verifies the integrity of the address buses connecting the processors to the
memory modules. Verification is done by writing data to all possible addresses that have only 1 bit
either set (1) or reset (0), having alternate bits set, having all bits high, and having all bits low. The
purpose of this test is to check for address lines that are either shorted to ground, shorted to a high-
voltage signal, shorted to other address lines, or floating (disconnected). This test alone might not
indicate a hard failure.
• Walk test—This test verifies the integrity of the data buses connecting the processors to the memory
modules. Verification is done by writing data to all possible addresses that have only 1 bit either set
(1) or reset (0), having alternate bits set, having all bits high, and having all bits low. The purpose of
this test is to check for data lines that are either shorted to ground, shorted to a high-voltage signal,
shorted to other address lines, or floating (disconnected). This test alone might not indicate a hard
failure.
• Noise test—This test verifies memory integrity by writing the inverse of the current test address to the
current test address. The current test address alternates between the start and the end of the current
test block, incrementing or decrementing the address until the entire block has been accessed. The
purpose of this test is to check for address and data bus transition problems when these lines are
forced high and low as rapidly as possible. A failure of this test indicates a failure of the DIMM.
• March test—This test is similar to a true walk bit test and is able to detect the following: address
faults, stuck-at faults, transition faults, coupling faults, and linked coupling faults. These types of faults
occur when memory cells within a bit cell array affect the operation of nearby memory cells. In many
cases, static type tests do not detect these failures. A failure of this test indicates a failure of the
DIMM.
• Random address test—This test verifies memory integrity by running a random pattern across a given
test range. The addresses used to store the patterns are selected randomly and normalized to fit
within the current test block. The purpose of this test is to detect intermittent memory problems that
can be caused by temperature, variable clock speeds, variable voltages, signal timing,
manufacturing faults, variable refresh rates, and decay. This test is also useful in detecting memory
faults that might not be detected by other static tests. A failure of this test indicates a failure of the
DIMM.
Not all the memory in a system can be tested because of the operating system and applications that are
installed. As a best practice, use the default setting for each test. The default settings help ensure the
maximum amount of memory that is available is tested.
To test memory thoroughly, run as many loops as possible in the time you are allotted. If time is critical,
and all memory tests cannot be run, then HP recommends running the Random Address test and the Noise
test. These two tests can catch the most errors.