Memory problems

Use this information to solve memory problems.

The memory problems and actions table with one level of row and column headers.

  • Follow the suggested actions in the order in which they are listed in the Action column until the problem is solved.
  • If an action step is preceded by "(Trained technician only)," that step must be performed only by a trained technician.
  • Go to the IBM support website at the IBM support portal to check for technical information, hints, tips, and new device drivers or to submit a request for information.
Symptom Action
The amount of system memory that is displayed is less than the amount of installed physical memory.
Note: Each time you install or remove a DIMM, you must disconnect the server from the power source; then, wait 10 seconds before restarting the server.
  1. Make sure that:
    • No error LEDs are lit on the operator information panel.
    • No DIMM error LEDs are lit on the system board.
    • Memory mirrored channel does not account for the discrepancy.
    • The memory modules are seated correctly.
    • You have installed the correct type of memory.
    • If you changed the memory, you updated the memory configuration in the Setup utility.
    • 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.
    • There is no memory mismatch when the server is at the minimum memory configuration.
  2. Reseat the DIMMs, and then restart the server.
  3. Check the POST error log:
    • If a DIMM was disabled by a systems-management interrupt (SMI), replace the DIMM.
    • If a DIMM was disabled by the user or by POST, reseat the DIMM; then, run the Setup utility and enable the DIMM.
  4. Check that all DIMMs are initialized in the Setup utility; then, run memory diagnostics (see Running DSA Preboot diagnostic programs).
  5. Reverse the DIMMs between the channels (of the same microprocessor), and then restart the server. If the problem is related to a DIMM, replace the failing DIMM.
  6. Re-enable all DIMMs using the Setup utility, and then restart the server.
  7. (Trained technician only) Install the failing DIMM into a DIMM connector for microprocessor 2 (if installed) to verify that the problem is not the microprocessor or the DIMM connector.
  8. (Trained technician only) Replace the system board.
Multiple DIMMs in a channel are identified as failing.
Note: Each time you install or remove a DIMM, you must disconnect the server from the power source; then, wait 10 seconds before restarting the server.
  1. Reseat the DIMMs; then, restart the server.
  2. Remove the highest-numbered DIMM of those that are identified and replace it with an identical known good DIMM; then, restart the server. Repeat as necessary. If the failures continue after all identified DIMMs are replaced, go to step 4.
  3. Return the removed DIMMs, one at a time, to their original connectors, restarting the server after each DIMM, until a DIMM fails. Replace each failing DIMM with an identical known good DIMM, restarting the server after each DIMM replacement. Repeat step 3 until you have tested all removed DIMMs.
  4. Replace the highest-numbered DIMM of those identified; then, restart the server. Repeat as necessary.
  5. Reverse the DIMMs between the channels (of the same microprocessor), and then restart the server. If the problem is related to a DIMM, replace the failing DIMM.
  6. (Trained technician only) Install the failing DIMM into a DIMM connector for microprocessor 2 (if installed) to verify that the problem is not the microprocessor or the DIMM connector.
  7. (Trained technician only) Replace the system board.
Parent topic: Troubleshooting by symptom