3 Sticks of RAM iMac 27" Late 2013

Discussion in 'iMac' started by Gazmo, Mar 25, 2015.

  1. Gazmo macrumors member

    Gazmo

    Joined:
    Nov 23, 2014
    Location:
    North Wales, UK
    #1
    Hi Guys,

    I'm after some advice please with RAM I am about to install into my late 2013 iMac.

    So it came preloaded with 2x 4GB and I've just bought 1 x 8GB from Crucial. Now my question is - am I able to install the 8GB in 1 slot and then keep the 2x 4GB in the same slots? Is it safe to do so?

    I plan to get another 8GB next month to have 2x 8GB and 2x 4GB = 24GB - would this setup still work in dual channel?

    Thanks.
     
  2. drambuie macrumors 6502a

    Joined:
    Feb 16, 2010
    #2
    If you leave the Apple 4GB DIMMs in their original slots and place the 8GB in the empty slot between them, you will have the optimal setup for 3 DIMMs. The setup should be:

    Slot 1 - 4GB
    Slot 2 - 8GB
    Slot 3 - 4GB
    Slot 4 - Empty

    The two 4GB DIMMs will work in dual channel mod, and the 8GB will be in single channel mode, with a slight 8 to 10% memory performance hit, only when accessing the upper 8GB. When you fill slot 4 with another 8GB the full 24GB will be in dual channel mode.

    Just make sure the 8GB modules are the exact match for the originals in frequency and CL latency.
     
  3. desantii macrumors 6502

    desantii

    Joined:
    Sep 9, 2006
    Location:
    Aurora, IL
  4. redheeler macrumors 603

    redheeler

    Joined:
    Oct 17, 2014
    #4
    You don't need it in pairs but there is a slight performance dip from not having matched pairs. Compare that to a G5 where not having matched pairs is as good as having no memory at all.
     
  5. lchlch macrumors 6502a

    Joined:
    Mar 12, 2015
    #5
    If you put in 3 sticks all the memory sticks will run on single channel mode. Which would result in a 3%~7% reduction in performance.
     
  6. Gazmo thread starter macrumors member

    Gazmo

    Joined:
    Nov 23, 2014
    Location:
    North Wales, UK

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