1. iMore Question's Avatar
    My new iMac 27" 5K came with 8GB memory: 2 x 4GB in slots 1 & 3 (counting down from top). I just added 16GB of Crucial memory: 2 x 8GB in slots 2 & 4. The iMac boots fine and recognizes all 24GB memory, and System Info (formerly System Profiler?) reports the following:
    4GB in BANK 0/DIMM0,
    8GB in BANK 0/DIMM1,
    4GB in BANK 1/DIMM0,
    8GB in BANK 1/DIMM1.

    However, an online forum post suggests that matching pairs should be in the same bank (pair in bank 0, pair in bank 1) for best performance. If so, why would Apple send it with the two 4GB modules in Banks 0 and 1? Should I re-order the modules to 4/4/8/8 or 8/8/4/4 rather than 4/8/4/8?

    Confused about memory pairings,
    Steve M.
    01-12-2016 11:15 PM
  2. robertk328's Avatar
    Welcome to iMore!

    If all the RAM is registered in System Info and your iMac is running ok without issue, I wouldn't worry about it. You could always switch them in the order mentioned if that helps you sleep at night, but I would be content to leave it alone as well. Enjoy your new iMac!
    01-13-2016 06:04 AM

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