Upgrade RAM in late 2009 27inch iMac

Discussion in 'iMac' started by Sensamic, Nov 29, 2015.

  1. Sensamic macrumors 68030

    Mar 26, 2010
    The late 2009 27inch iMac uses 1067 MHz DDR3.

    I don't see 1067 MHz anymore. All I see are:

    - DDR3 1333

    - DDR3 1600

    - DDR3 1866


    Which one should I buy to upgrade my iMac from 4GB RAM to 10GB? My plan is to buy an 8GB stick and use the 2GB stick on the other slot. Not sure if my iMac has 2 or 4 slots.

    What would you guys recommend? I'm buying locally (on a pc shop), not online.

  2. DeltaMac macrumors G3


    Jul 30, 2003
    Your 2009 iMac 27-inch has 4 slots.
    Technically, it's 1066 MHz, not 1067, but should work fine.
    If you are purchasing a single 8GB stick, there's no reason to remove either of the 2GB sticks already in place.
    Add the 8GB in either of the empty slots, which would give you a total of 12GB!

    Some Macs that use that PC3-8500 can be picky about what works and what doesn't - but you should be able to use the PC3-10600 (1333 MHz)
    Here's Apple's support page for installing memory on your iMac
  3. MadDane macrumors 6502a

    Apr 5, 2015
    I also have a late 2009 27" iMac. I have installed 20GB of RAM, all 1333 MHz. It works like a charm. I have 2x8GB plus 2x2GB in my machine. Though Apple never acknowledged this the late 2009 27" works with up to 32GB RAM. At least I know this is true for the i7 model that I have.
  4. ribbo1939 macrumors newbie

    Feb 8, 2009

    If its any consolation, I have a 27" late 2009 iMac and recently installed 2 x 8GB RAM into the vacant slots giving a total of 20GBs of RAM. Not had any problems for past couple of months since I did this.
  5. Sensamic thread starter macrumors 68030

    Mar 26, 2010
    Great. Thanks guys.

    My only doubt was which specific variant to buy. It seems 1333 MHz is the one to win. I'll buy that.


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