iMac 2011 Memory Upgrade Slower Benchmark

Discussion in 'iMac' started by mattkidd, Aug 23, 2011.

  1. mattkidd macrumors regular

    mattkidd

    Joined:
    Aug 6, 2008
    Location:
    United Kingdom England Northants
    #1
    Hey Guys!

    Just upgraded my baseline 2011 21.5 from 4GB of RAM to 8GB of Ram for £20 through crucial.

    After installing the ram decided to run some benchmarks on geekbench the result was a lower score than previously taken, the processor scored higher than before however the memory scored much lower. I then booted up Windows 7 via bootcamp to see if there was any difference in the windows index score and again it decreased by 0.3 on both CPU and RAM. Why is this?

    My slots are currently:

    Slot 1 - 2GB (Apple)
    Slot 2- 2GB (Apple)
    Slot 3 - 4GB (Crucial)
    Slot 4 - None

    Help would be much appreciated ;)
     
  2. nOw2 macrumors regular

    Joined:
    Sep 1, 2009
    #2
    The memory system is dual channel which requires matched pairs, as per the original Apple DIMMs. Installing an unmatched pair drops the access to single channel model which will affect memory access speed.
     
  3. BeamWalker macrumors 6502

    BeamWalker

    Joined:
    Dec 18, 2009
    #3
    Since you have only a single RAM Module installed the whole system is not running in Dual Channel anymore - hence it's slower.
     
  4. mattkidd, Aug 23, 2011
    Last edited: Aug 23, 2011

    mattkidd thread starter macrumors regular

    mattkidd

    Joined:
    Aug 6, 2008
    Location:
    United Kingdom England Northants
    #4
    Ahhh right i thought this may be the case, so would i need to buy another 4GB stick in order to get true 8GB of memory at the right speed? :cool: and if so would i get the correct dual speed by keeping both 2GB sticks and two 4GB sticks in the system, giving me 12GB?
     
  5. aliensporebomb macrumors 68000

    aliensporebomb

    Joined:
    Jun 19, 2005
    Location:
    Minneapolis, MN, USA, Urth
    #5
    Yes

    Yes that would work and correct the dual channel issue.
     
  6. mattkidd thread starter macrumors regular

    mattkidd

    Joined:
    Aug 6, 2008
    Location:
    United Kingdom England Northants
    #6
    That's great, Cheers for your help guys ;)
     
  7. accessoriesguy macrumors 6502a

    Joined:
    Jul 8, 2011
    #7
    I did not think dual channel would make such a difference, guess it's kind of like raid for hard drives.
     

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