Late 2015 iMac: New ram of same specs, not playing nice with old

Discussion in 'iMac' started by maves, Sep 30, 2018.

  1. maves macrumors newbie


    Sep 30, 2018

    I recently bought 2x8gb @1867ghz sticks of RAM to add to the 16gb (also 2x8gb @1867ghz) that is in my late 2015 iMac.

    Despite tracking down RAM that is the same brand, clock speed, and latency; when installed together, the system shows the speed as 1333ghz.

    I've attached a picture of the old and new RAM. Is there something I'm missing? Is there any reason these sticks should not be completely compatible?


  2. droog Suspended


    Apr 10, 2018
    Try using the new ram independently of the original ram. If it boots to 1867, then their is a good chance the imac down clocks while running quad channel. If this is so, you'd need 2x16 to reach 1876. You'll probably be fine at 1333 unless you are doing a bunch of gaming.
  3. robbier macrumors member

    Apr 27, 2008
    I would also try a PRAM reset and then see if the RAM is running at the proper speed.
  4. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    Where did you get the modules? OWC and Crucial for me.

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3 September 30, 2018