iMac Retina 5K slower after adding more RAM?

Discussion in 'iMac' started by frozen220, Aug 10, 2016.

  1. frozen220 macrumors member

    Jun 29, 2007
    OK so I just got my 27 inch iMac Retina 5K, 4 GHz. Shipped with just 8 GB of OEM RAM, and instead of paying an arm an leg for Apple's upgrade to 16 GB, went ahead and bought 2 8 GB RAM sticks from Crucial for the system.

    After realizing there were 4 total slots, that I could actually keep the OEM and add my 16 GB for a total of 24 GB, thats what I did. When I opened the RAM compartment I notice they had the existing 2 4 GB OEM sticks in alternating slots (Slot 1 used, Slot 2 empty, Slot 3 used, Slot 4 empty) -- which I thought was odd... so I went ahead and moved one of them so Slot 1 and 2 are the 4 GB OEM sticks. Then in Slot 3 and 4 I put the 2 8GB Crucial sticks.

    Booted the computer. Everything seems fine. Open About this Mac, says 24 GB installed. Great.

    OK so i wanted to compare Geekbench results before and after the memory upgrade, so before I added the new RAM I did a test (32-bit, the free version). Of course no apps open at all.

    Then after I installed the new RAM I did another Geekbench (again, no apps open).

    Can someone tell me why the Geekbench scores for BOTH processor AND Memory are LOWER now?

    Pre-Upgrade scores:
    Single-core: 4032 / Multi-core: 15355 / Memory Performance Single-Core: 3501 / Memory Performance Multi-core: 3582 -- the memory speeds are reading between 14.1 GB/sec to 15.9 GB/sec going from Stream Copy to Stream Triad.

    NOW, compare to scores AFTER memory upgrade:

    Single-core: 3680 / Multi-core: 14950 / Memory Performance Single-Core: 2184 / Memory Performance Multi-core: 2141 -- the memory speeds are reading between 8.66 GB/sec to 9.66 GB/sec going from Stream Copy to Stream Triad.

    Does anyone know what is going on? Yes, I've triple checked, I bought the correct and recommend RAM from Crucial for this iMac. Does the slots and the arrangement of OEM vs Crucial have something to do with it? Is the OEM not compatible with Crucial? Should I just use the Crucial and live with 16 GB like I originally expected anyways?

    Any advice would be appreciated!!! Thank you!!!
  2. crouchingtiger macrumors member

    Feb 15, 2004
    Yes, move the Apple sticks back to their original slots and use your matched set in the other two slots and it will be fine.

    Pairing up the slots like this in both Macs and PCs enables faster memory access.

  3. tdhurst macrumors 601


    Dec 27, 2003
    Phoenix, AZ
    Put them back where you found them and insert the new chips in the open slots.
  4. frozen220 thread starter macrumors member

    Jun 29, 2007
    Thank you! It is now faster!
    --- Post Merged, Aug 10, 2016 ---
    Thank you!!!!

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