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DIMM and SPD mapping

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  • DIMM and SPD mapping

    Is there any correlation between the order MemTest reports the SPDs and DIMMs? I’ve been able to determine the SPD to DIMM physical slot on my particular server by comparing the serial numbers.
    If I pull two modules from the board of 24 slots, MemTest reports that Dimm #X and Dimm #Y empty and will obviously report that it only found 22 SPDs.
    my issue is that the SPDs will be numbered 0-21 regardless of which 2 slots are empty and I’m no longer able to map SPD # to physical slot.

  • #2
    What's the purpose of trying to match the SPD read order with the physical slots?
    I don't think there is any universal rule for this. i.e. it might be different for different systems.

    The SPD data is read from the SMBus and each device on the SMBus has an address. So using the address it would probably be possible to work out the relationship for a particular system. But I don't think the SMBus address is being exposed for each RAM stick in the log.

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    • #3
      We are only using a single system type and attempting to map the results to the physical layout of the server to expedite finding DIMMs we want to remove. The MemTest report lists the Serial number with the SPD # so that is the simplest means of mapping.

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      • #4
        map the results to the physical layout of the server
        But wouldn't that involve a memory address decode ?
        Or are you referring to ECC corrected errors?

        Can you send a screen shot showing what you are referring to?

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        • #5
          Yes, this is for ECC errors.
          First image is when all 24 DIMMs are present and detected by MemTest. Based on past runs and examining the serial numbers we are able to map SPD # to physical DIMM slot on this particular mother board/server.
          The 2nd picture shows when a DIMM is not detected. It will list 23 SPDs, 0-22, regardless of which DIMM #. In this case I pulled the physical DIMM (CPU #1, Slot 5 on our board) which is normally associated with SPD #10. MemTest reports that DIMM slot OSForensics / OSFMount / OSFClone is empty.

          So I am looking for a means to either associate MemTest DIMM number to the predictable SPD number in the report or advice on how to map MemTest DIMM Slot number to our particular as the info assoicated with the Dimm Slot number in the report is not helpful, at least on this board, at identifying the physical slot.
          Click image for larger version

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          Click image for larger version

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