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Thread: Memory Upgrade

  1. #1
    Memory Upgrade
    What is the most efficient 32 GB memory configuration for a 2019 27" iMac? Would it be 4 X 8 GB DIMMS or 2 X 16 GB DIMMS? i would think there would be some advantage to having the memory allocated between a 2 X 16 GB configuration but I really don't know how the iMac actually utilizes memory.

  2. #2
    Memory Upgrade
    jasongoldworthy's Avatar
    Member Since
    Aug 28, 2017
    Location
    Wales, UK
    Posts
    141
    Your Mac's Specs
    iMac Late 2009 32GB Intel Core i7 27" OSX 10.13.6
    hi there.


    and welcome to the forum


    as a rule its based on choice if the Mac supports the ram in 16GB dimms you could always get the 2 sticks as you said and that way you have room for another 2 in the future if you should need 64GB of ram.
    Mac Pro 4,1 Upgraded To 5,1
    32GB Ram
    Mac OSX 10.14.5
    512GB NVME 2TB 2TB 2TB HDD

  3. #3
    Memory Upgrade
    ferrarr's Avatar
    Member Since
    May 21, 2012
    Location
    Pawtucket, RI, US
    Posts
    6,221
    Your Mac's Specs
    L2014 Mac mini macOS 14, iPhone 8+ iOS 12, 12.9" iPad Pro 1 iOS 12, Pencil 1
    Are you buying the ram after you get the iMac? Then add the 16GB to the 2-4GB rams already installed?
    -- Bob --
    Please backup. Everything has a life cycle, unexpected and warning free. Nothing will last as long as you want it to.

  4. #4
    That would be my plan, but I guess I don't understand how a Mac accesses memory. For instance does the CPU just see 32 GB or does it search in say slot 1, then accesses slot 3 next if it needs more resources, then slot 2, etc?

  5. #5
    Memory Upgrade
    chscag's Avatar
    Member Since
    Jan 23, 2008
    Location
    Keller, Texas
    Posts
    57,876
    Your Mac's Specs
    2017 27" iMac, 10.5" iPad Pro, iPhone 7+, iPhone 8, Numerous iPods, Mojave
    No, the memory is contiguous. You can populate the top slots or bottom slots, doesn't matter. Apple, however, populates the top slots from the factory. Your new iMac will come standard with 2 x 4 GB modules located in the top slots.

    Probably best to do what Bob recommended. Leave the 8 GB that Apple installs and then add whatever configuration you wish to the bottom slots. Just make sure you buy the memory modules in pairs.

  6. #6
    Memory Upgrade
    pm-r's Avatar
    Member Since
    Oct 16, 2010
    Location
    Brentwood Bay, BC, Canada
    Posts
    11,409
    That would be my plan, but I guess I don't understand how a Mac accesses memory.

    You don't need to worry about it with that iMac model. It will use whatever RAM is available that's installed in any of the slots. No pairing etc needed:
    Canada RAM sells memory in Canada - Apple Macintosh iMac intel Core2Duo, CoreDuo 17", 20" and 24" (excellent local Mac supporting Canadian dealer)


    - Patrick
    ======

  7. #7
    Thanks, the answer I was looking for! Much appreciated.

  8. #8
    Quote Originally Posted by rde View Post
    That would be my plan, but I guess I don't understand how a Mac accesses memory. For instance does the CPU just see 32 GB or does it search in say slot 1, then accesses slot 3 next if it needs more resources, then slot 2, etc?
    The 4 slots are tied to a memory bus and whichever slots have memory sticks is added to the total pool. The memory is appropriately offset (handled by the hardware) such that the OS sees the pool, now how they are broken up by slots. For all practical purposes, RAM that is meant to work with your machine will operate the same regardless of how big or small it is. The larger stick just gives you more memory that is all.
    --
    Regards
    ...Ashwin


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