OWC 1867Mhz RAM runs at 1600 on 27" iMac Late 2015

Discussion in 'iMac' started by ahnl, Nov 3, 2015.

  1. ahnl macrumors newbie


    Nov 3, 2015
    I have an iMac 27" late 2015 / i7 with 8GB Apple Ram.

    Apple memory runs at 1867Mhz fine. When I add two 8GB OWC 1867Mhz RAMs, they all run at 1600.

    Any hints what the problem could be?
    - Apple RAM: 1867
    - I tried just the OWC's: 1600
    - I tried just OWC's in slots 1&2, and in 1,3: 1600
    - I tried Apple RAM in slots 1 & 2, OWC in 3 & 4: 1600
    - I tried Apple RAM in slots 1 & 3, OWC in 2 & 4: 1600




    Schermafbeelding 2015-11-03 om 20.28.35.png
  2. bankshot macrumors 65816


    Jan 23, 2003
    Southern California
    If the OWC memory ran at 1867 MHz by itself, I would say the issue is likely mismatching CAS latency (CL). As discussed in other threads, the memory controller will drop all modules to 1600 MHz if CL of one set is too fast for the other set to run at 1867. For example, Apple RAM is CL13, and people (including myself) who bought 1867 MHz CL11 RAM to pair with it saw a drop to 1600 MHz because the Apple RAM can only do CL11 (or 10) at that speed. The memory controller apparently prioritizes CL over clock frequency.

    However since you say the OWC is 1600 by itself, I would contact OWC.
  3. florinbss2 macrumors newbie

    Oct 30, 2015
    Memoirs using false advertising. In fact the factory is 1600 MHz.
  4. tdbrown75 macrumors member


    Apr 28, 2015
    Dallas, TX
    I'm running OWC's 16GB kit (2x8) and mine is running at 1867Mhz without issue.

  5. ohsnaphappy macrumors regular


    Jan 14, 2013
    I just don't mix ram. Some people get away with it. But with my luck, I won't even try it
  6. Sirmausalot macrumors 6502a


    Sep 1, 2007
    I had OWC send me the wrong RAM once. They were a huge PITA about it. I had another issue with defective hardware from them, again, terrible customer service.

  7. gsingham macrumors 6502

    Oct 20, 2013
    Yes because as mentioned in the other thread, the OWC run at CL11 @ 1867, the stock apple run at CL 13 @ 1867

    Now the imac like to match CL instead of frequency so it downs all CL11, unfortunately the stock apple runs at CL 11 @ 1600mhz only.

    I have also read that apple uses different suppliers for their base ram. If some are able to mix apple ram and get 1867mhz then chances are those stock rams are faster and can run @ CL11
  8. Buerkletucson, Nov 3, 2015
    Last edited: Nov 3, 2015

    Buerkletucson macrumors 6502


    Sep 12, 2015
    Great experience with OWC RAM
    OWC 2 x 8GB kit........along with Apple 2 x 8GB stock RAM.
    Works fine @ 1867Mhz.

  9. OWC Dyllon macrumors newbie

    OWC Dyllon

    Nov 4, 2015
    Woodstock, IL

    Thank you so much for your great post. At this time this has been confirmed as a programming issue in a few selected 8GB RAM units. Please reach out to OWC by phone, email or chat and we will be happy to get a replacement set up for you!

    OWC Dyllon


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