iMac 2017, *must* the RAM be 2400MHz?

Discussion in 'iMac' started by Woodlandjustin, Jun 3, 2019.

  1. Woodlandjustin macrumors member

    Jan 21, 2007
    For 27-inch 2017 iMac, the apple support page says
    Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:
    • PC4-2400 (19200)
    • Unbuffered
    • Nonparity
    • 260-pin
    • 2400MHz DDR4 SDRAM
    I see on a lot of RAM on Amazon, then give the choice of either 2400MHz or 2666MHz. I'm guessing the higher number is better, and so am wondering, is the 2017 model merely designed for the old 2400MHz, but can work better if the 2666MHz is used instead; or, is it simply a compatibility issue, that either the 2666MHz won't work, or that it will work but no better than the 2400MHz due to limitations and so is not worth paying extra for the 2666MHz RAM?

    If the answer is that it's best to get 2666MHz, then I'm considering this:

    Good choice?

  2. kazmac macrumors 604


    Mar 24, 2010
    On the silver scream
    I went with the recommended 2400.

    Bought the crucial 32gb set on Amazon and installed in my new 2017.

    Cannot answer if the 2666 will work in the 2017. Maybe someone else will chime in.
  3. jwhazel macrumors regular

    Sep 22, 2005
    This one.
  4. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    You got it right faster memory will work at the 2400 speed.
  5. Woodlandjustin, Jun 4, 2019
    Last edited: Jun 4, 2019

    Woodlandjustin thread starter macrumors member

    Jan 21, 2007
    Thank you to everyone for replying, all input very helpful!
    Hmm, on that thread you wrote:
    "I'd rather buy the 2666MHz ram instead of the 2400MHz ram in case I upgrade to the 2019 27-inch iMac."​

    I just got this computer, so I'm not planning to upgrade for like 6 years maybe? That's why I'm upgrading this to 40GB of RAM, a 1TB PCIe SSD and a 2GB SATA SSD - hopefully that will make it last at least 6 years. So by then, the 2666MHz will also likely be in need of upgrading for the next 6 years, right? After all, 4266MHz is already available, such as the Corsair Dominator Platinum.

    So if this is true:
    then I don't see the advantage of spending the extra money to get something which will not perform better and will be just as out of date in 6 years time. Or is there something I'm missing?
    --- Post Merged, Jun 4, 2019 ---
    Also, anyone have info on Crucial vs. Corsair?
    The Corsair is actually a few pounds cheaper, and I seem to be reading very good things about it on the net. Here are the two I'm considering:
    EDIT: sorry, that was the 2666MHz version of the Corsair. It's still cheaper than the Crucial 2400MHz, but I'm struggling to find the Corsair 2400MHz version. But if this 2666MHz Corsair is cheaper than the Crucial 2400MHz, maybe better choice anyway? Searching for the 2400MHz version.... ok so here it is:

    So that's:
    Crucial 2400MHz - £149.57
    Corsair 2666MHz - £146.47
    Corsair 2400MHz - £142.47

    I hope I made the right two choices but if I made a mistake or if there are better choices, I would really love to hear about it! Many thanks, hoping my choices will be right to see me through the coming years!
  6. Woodlandjustin, Jun 4, 2019
    Last edited: Jun 4, 2019

    Woodlandjustin thread starter macrumors member

    Jan 21, 2007
    Also one question about this - if I want to keep the 8GB of 2400MHz that came with it, if I use 32GB of 2666MHz will that be an issue, the two being different like that? I'm considering that if it's only £4 more for 2666MHz then if I sell them off in future there might be some slight advantage, and if their is no other disadvantage to using 2666MHz, perhaps I should. So it's important to know if it would cause issues with my 8GB of 2400MHz. If mixing is not good, then it would seem the 2400MHz would be the clear choice - 40GB of 2400MHz would be better than 32GB of 2666MHz.

    Overall I'm sensing the Corsair 2400MHz - £142.47 may be the best option:
  7. kazmac macrumors 604


    Mar 24, 2010
    On the silver scream
    I think that will be an issue, but once again hopefully someone else will chime in.

    FWTW, my stock 2017 with 2TB fusion drive and 40gb of 2444 ram is flying. Very fast.
  8. jwhazel macrumors regular

    Sep 22, 2005
    Not an issue Max speed on the 2017 is 2400. From there, computer will set ram speed to the slowest ones installed which in your case will be the stock 2400. If you throw a stick of 2100 in there, it will set everything to 2100 and so on.
  9. Kyousuke macrumors newbie


    Mar 25, 2019
    Halifax, NS
    Just received my crucial (32GB kit) for my iMac 2017 today. Took 5 minutes to install. Booted up with no problems at all.
    I now have 48GB ram total :)
  10. kwikdeth macrumors 65816

    Feb 25, 2003
    Tempe, AZ
    there's a small, very small chance they might not play nice together, but generally speaking you should be fine. it certainly wont break the computer; it just might not boot with both installed. it more has to do with how the modules are constructed than their speed.

Share This Page

10 June 3, 2019