Rank

DIMM (Memory/RAM) Population Procedure

Today, we’ll discuss about the physical installation of the Dual In-line Memory Module (DIMM) into the servers. DIMMs are most commonly known as a Memory/RAM stick.

Here are a few quick guidelines, which are not tied to any specific server hardware vendor:

  1. Install RAM DIMM modules in accordance with the processors installed.
  2. Every processor has a few channels and every channel has a few slots.
  3. White slots always indicate the start of a channel.
  4. Do not install DIMM modules in the channel slots for a processor (say, for example, Processor 2, 3 or 4) if the processor itself is not present (not installed).
  5. Always install DIMM modules first in the white slots, i.e., the start of each channel for a processor. Then proceed towards the next slot (black[s]) in the same order, i.e.
    Example for a single processor (Processor 1):
    a. Channel 1-white slot, Channel 2-white slot, Channel 3-white slot…Channel N-white slot.
    b. Channel 1-black slot, Channel 2-black slot, Channel 3-black slot…Channel N-black slot.
    c. Channel 1-2nd black slot, Channel 2-2nd black slot, Channel 3-2nd black slot…Channel N-2nd black slot.
    d. So on and so forth.
  6. A few other rules regarding types of DIMMs: UDIMMs (Unbuffered), FBDIMM (Fully Buffered), RDIMMs (Registered), LRDIMMs (Load Reduced) and NVDIMMs (Non-Volatile) should be read. Former 2 are rarely used in the newer generation server architectures. Latter 3 are commonly used.
  7. DIMMs should be installed rank-wise, for instance, quad-rank DIMM should be installed before dual-rank DIMM and single-rank DIMM.
    Note: Memory Capacity doesn’t matter but Rank does matter.
  8. Mixing of different types is not recommended as well as not supported in some scenarios. Do refer the document of the server hardware vendor before mixing 2 types.
  9. You will be able to check the total RAM installed into the system during the server boot.
    If you find the amount of RAM to be incorrect, check whether you have installed RAM correctly as mentioned above.

On the inside of the panel which opens the server, of any form of server (rack, tower or blade), you will find short instructions on memory population, along with the server architecture diagram, which come in handy at times.

Further reading and references used in this post:

  1. DDR3 and HPE ProLiant Gen8: http://h20565.www2.hpe.com/hpsc/doc/public/display?docId=emr_na-c03293145
  2. DDR4 and HPE ProLiant Gen9: https://h20564.www2.hpe.com/hpsc/doc/public/display?docId=emr_na-c05240460
  3. DD4 and HPE ProLiant Gen10: https://h20195.www2.hpe.com/v2/GetDocument.aspx?docname=a00017079enw