Help on memory upgrade

Discussion in 'iMac' started by dcaccount, Aug 4, 2019.

  1. dcaccount macrumors regular

    Joined:
    Nov 17, 2013
    #1
    Hello,

    I have purchased a 27” iMac with 8GB ram and I want to upgrade it. I have found the crucial memories but I have a doubt, single rank or dual rank?

    Can anyone please explain the difference between single and dual rank and what one suits the 2019 iMac?

    Thanks a lot,
    Dan
     
  2. priitv8 macrumors 68040

    Joined:
    Jan 13, 2011
    Location:
    Estonia
    #2
    I think both will work.
    I’ve also installed the Crucial dual-rank modules, but the apple ones I pulled, clearly state they’re single rank.
    Someone correct me, if I’m wrong....
    A20133A6-085B-48C9-8270-6FA07E8ECC3C.jpeg 8992A8DD-D310-4C50-84B8-5301ADC7830D.jpeg
    Long story short - the crucial ram on the pic definitely works, also in combination with factory 4GB dimms.
     
  3. dcaccount, Aug 4, 2019
    Last edited: Aug 4, 2019

    dcaccount thread starter macrumors regular

    Joined:
    Nov 17, 2013
    #3
    Thanks for replying. Can you please advise the P/N of the 16GB ram that you installed or even better the link to the shop where you purchased it from?

    By the way, what is the difference between single and dual rank modules?
     
  4. priitv8 macrumors 68040

    Joined:
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    Estonia
    #4
    Sure, I posted them here: https://forums.macrumors.com/thread...he-new-2019-imac.2174176/page-9#post-27552646
    Its about how the chips are organised for addressing.
    https://en.wikipedia.org/wiki/Memory_rank
    In general, more ranks seem to be better:
    https://forums.lenovo.com/t5/ThinkP.../Memory-dual-rank-vs-single-rank/td-p/3698242
    https://serverfault.com/questions/6...en8/setup_install/advanced/Content/138678.htm

    It is important not to mix differently ranked modules on same channel (on iMac it means the alternating slots. 8GB from factory came in slots 0 and 2, slots 1 and 3 were empty, where I installed crucial 16GB DIMMs for a total of 40GB RAM). Later I also swapped the apple DIMMs for another pair of crucials for a total of 64GB.
     
  5. dcaccount thread starter macrumors regular

    Joined:
    Nov 17, 2013
    #5
  6. priitv8 macrumors 68040

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    Jan 13, 2011
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    Estonia
    #6
    No, first I read users comments both here and on amazon, then I installed 32 into my 2019 iMac.
    Did not experience any issues. So I upgraded to full 64.
    Intel Macs do not use any special or proprietary RAM, so as long as the specs are met, it is OK to go. User installable part as well.
    AFAIK, amazon offers you also a return window, should you order a wrong set.
    But this particular kit has been reported problem free with 2019 iMacs several times on the web, so I went from there.
    Screenshot 2019-08-04 at 19.15.53.png Screenshot 2019-08-04 at 19.16.05.png
     
  7. dcaccount thread starter macrumors regular

    Joined:
    Nov 17, 2013
    #7
    Thanks, last question. You confirm that the correct P/n to be ordered is:


    CT2K16G4SFD8266 Dual rank?

    Thanks again,
    Dan
     
  8. max23 macrumors newbie

    Joined:
    Aug 4, 2019
    #8
    Hi, I also have a question ... can I install only a 16GB module that you attach in photo of crucial? or it is necessary to install two of them in pairs. My idea is to add one 16gb module to Apple's 8gb modules and I leave a place to add another 16 later? Is it possible or not
    thank you
     
  9. priitv8 macrumors 68040

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    Jan 13, 2011
    Location:
    Estonia
    #9
    That's the one.
     
  10. priitv8 macrumors 68040

    Joined:
    Jan 13, 2011
    Location:
    Estonia
    #10
    I have not tried it on mine, but according to this source, it is not a must, but highly recommended:
    https://superuser.com/questions/109308/why-does-ram-need-to-be-installed-in-pairs
     

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9 August 4, 2019