iMac RAM compatibility help & advice

Discussion in 'iMac' started by AdamWarby, May 29, 2017.

  1. AdamWarby macrumors newbie

    Apr 23, 2015

    Looking for a little bit of help; searched around the forums but couldn't see this question asked (apologies if it has).

    I have a late-2012 iMac with 8GB (2 x 4GB) of stock RAM, and I've added 16GB (2 x 8GB) myself. It's DDR3 @ 1600 MHz I believe.

    I've today bought a new iMac (late-2015 model) with 8GB stock RAM. I believe this is DDR3 @ 1833 MHz.

    I want to know if I can take the RAM out of my old iMac, and put it into the new one despite the MHz difference? Also, are there any implications of using 2 x 4GB and 2 x 8GB inside the same machine? If not, what order would you slot them into the machine (is there a preferential ordering?)?

    Thanks for any help and support, appreciated.

  2. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    All you will achieve is slowing down then iMac as the 1867MHz modules will be strangled back to 1600MHz, no matter how you install them. You spent a pretty penny on the new iMac, so lash out on proper memory from Crucial or OWC.
  3. AdamWarby thread starter macrumors newbie

    Apr 23, 2015
    Okay, got it, thank you.

    If the iMac has 8GB, would you only go up in 8GBs? So have 4 x 4GB, or is 2 x 4GB and 2 x 8GB okay?
  4. loekf macrumors 6502a


    Mar 23, 2015
    Nijmegen, The Netherlands
    For DDR memory I would always put memory with the same speed and timing (RAS, CAS) in the 4 slots. Also remember it works best if you've the same type in pairs. E.g.

    Slot A : 4 GB 1866 MHz, CL12
    Slot B : 4 GB 1866 MHz, CL12
    Slot C : 4 GB 1600 MHz, CL10
    Slot D : 4 GB 1600 MHz, CL10

    is not very smart, you will loose performance.

    An iMac is an investment for years, given the lengthy support of OS X, so you if can afford buy 4 x 8 GB 1866 MHz and fill it up to the max. Preferably buy from Crucial or Corsair.
  5. AdamWarby thread starter macrumors newbie

    Apr 23, 2015
    Thanks, really appreciate your help.

    I don't have enough money to brim it yet (I just shelled out for the top-end machine so a bit short of cash). If I wanted to add 2 x 4GB to match what's in the machine already, what make would you go for, or does it not matter?
  6. DeltaMac macrumors G3


    Jul 30, 2003
    You can add 2 x 4GB, 2 x 8GB, or even 2 x 16GB to your Late 2015 iMac, which can be upgraded to 64GB of RAM, should you feel a need for that much...

    I usually order from Data Memory Systems.
    Good memory that you can be sure about, and a decent price, too.
    How can you go wrong?
  7. AdamWarby thread starter macrumors newbie

    Apr 23, 2015

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