Memory Problems - IBM 7985 Problem Determination And Service Manual

Memory problems

v Follow the suggested actions in the order in which they are listed in the Action column until the problem
is solved.
v See Chapter 4, "Parts listing, System x3655, Type 7985 and 7943," on page 93 to determine which
components are customer replaceable units (CRU) and which components are field replaceable units
(FRU).
v If an action step is preceded by "(Trained service technician only)," that step must be performed only by a
trained service technician.
Symptom
The amount of system memory
that is displayed is less than the
amount of installed physical
memory.
Multiple rows of DIMMs in a
failing branch are identified as
failing.
Action
1. Make sure that:
v No error LEDs are lit on the operator information panel.
v Memory sparing does not account for the discrepancy.
v The memory modules are seated correctly.
v You have installed the correct type of memory (see "Installing a memory
module" on page 132).
v If you changed the memory, you updated the memory configuration in the
Configuration/Setup Utility program.
v All banks of memory are enabled. The server might have automatically
disabled a memory bank when it detected a problem, or a memory bank
might have been manually disabled.
2. Check the POST error log for error message 289:
v If a DIMM was disabled by a systems-management interrupt (SMI), replace
the DIMM.
v If a DIMM was disabled by the user or by POST, run the Configuration/Setup
Utility program and enable the DIMM.
3. Run memory diagnostics (see "Running the diagnostic programs" on page 55).
4. Make sure that there is no memory mismatch when the server is at the
minimum memory configuration (two 512 MB DIMMs).
5. Add one pair of DIMMs at a time, making sure that the DIMMs in each pair
match. Install the DIMMs in the sequence described in "Installing a memory
module" on page 132.
6. Reseat the DIMMs.
7. Replace the following components one at a time, in the order shown, restarting
the server each time:
a. DIMMs
b. (Trained service technician only) System board
1. Reseat the DIMMs; then, restart the server.
2. Remove the lowest-numbered DIMM pair of those that are identified and
replace it with an identical pair of known good DIMMs; then, restart the server.
Repeat as necessary. If the failures continue after all identified pairs are
replaced, go to step 4.
3. Return the removed DIMMs, one pair at a time, to their original connectors,
restarting the server after each pair, until a pair fails. Replace each DIMM in the
failed pair with an identical known good DIMM, restarting the server after each
DIMM. Replace the failed DIMM. Repeat step 3 until you have tested all
removed DIMMs.
4. (Trained service technician only) Replace the system board.
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Chapter 3. Diagnostics