Re-using RAM

Discussion in 'iMac' started by norman21, Jun 3, 2011.

  1. norman21 macrumors newbie

    Joined:
    May 5, 2009
    #1
    Our household has multiple iMacs and I am planning to upgrade memory:
    from 2009 iMac 10,1 memory 2GB DDR3 1067 MHz (2 off - total 4MB)
    from 2008 iMac 8,1 memory 1GB DDR2 800 MHz (2 off - total 2MB)
    from 2006 iMac 6,1 memory 1 GB DDR2 667 MHz (1 off - total 1MB)

    To what extent, if at all, can I upgrade the memory of the newest machine and trickle down the old RAM form that m/c to the older m/c? In particular, will the DDR3 memory chips from the 2009 iMac work in the 2008 iMac - even though the 2008 iMac only requires DDR2? i.e. is it the case that the DDR3 has capabilities for speed that the 2008 iMac will not take advantage of, or will it simply not work at all.

    Similarly, can surplus memory be passed from the 2008 iMac to the 2006 iMac?


    TIA

    Norman
     
  2. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #2
    Take a look at the RAM specs for the machines on http://www.everymac.com/. If they are the same you can move RAM between the machines, if not you can't.
     
  3. norman21 thread starter macrumors newbie

    Joined:
    May 5, 2009
    #3
    I am well aware the specs are different (as detailed in my original post). That is, I know the 2008 model machine has a spec of DDR2 - but I wonder does that mean that the DDR3 will NOT work at all, or just that DDR2 is preferred, and while DDR3 is newer, faster (and originally more expensive) it is not worth buying this super memory for the older machine.
     
  4. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #4
    DDR3 is physically incompatible with DDR2. They do this to prevent damage from sticking electrically incompatible sticks into the wrong slots. So in short you cannot use DDR3 in a DDR2 machine.
     
  5. norman21 thread starter macrumors newbie

    Joined:
    May 5, 2009
    #5
    Thank you - for the bad news! Sounds like I shall have to buy extra DDR and extra DDR3 ; Oh well - keeps the economy motoring along.

    But can I use surplus 800MHz DDR2 memory in the 2006 machine that only 'needs' 667MHz DDR2?
     
  6. philipma1957 macrumors 603

    philipma1957

    Joined:
    Apr 13, 2010
    Location:
    Howell, New Jersey
    #6
    if you have a pair of 2gb sticks in the 2009 leave them in add the pair of 4gb sticks in and you will have 12gb in your 2009 imac.

    the mac 8.1 can take a 4gb stick


    the mac 7.1 may work with the pair of 1gb sticks from the mac 8.1



    so you have the 2009 with 12gb you added 8gb and left the pair of 2gbs in. this will work I have a pair of 1gb's and a pair of 4gb's in my imac

    the 2008 has 1 stick of 4gb this will work


    the 2007 has the two sticks fro the 2008 for a total of 2gb I think this will work. you can test it for free. as you have the 2 sticks in your 2008.
     
  7. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #7
    In theory yes, the faster RAM should just down clock. In some cases this doesn't work (but it can't damage the machine so you should be safe to try this).
     

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