Adding RAM

Discussion in 'Mac Basics and Help' started by kenglade, Apr 13, 2010.

  1. kenglade macrumors 6502

    Dec 20, 2008
    I just upgraded from an iMac G5 to an iMac 21.5" with 2x2.0GB of RAM. That leaves me two empty memory slots. If I want to add more memory can I just put in another 1x2.0GB RAM? Is it possible to mix memory modules in case I want to add 2x4.0 GB modules or do they all have to be the same size?
  2. Peruvian macrumors regular


    Jun 10, 2006
    I changed the ram in my Imac 24in and theres was only 2 slots, not 4.. Unless they have changed the newer models..
    Also I was always told to keep the ram sticks the same, not mix and match..
    Not sure how it would affect performance if they were mixed...
  3. -Ryan- macrumors 68000

    Jan 28, 2009
    Nope, you can add whatever amount of RAM you want to the computer, however, you should install the RAM in pairs. The reason for this, is because it is dual channel, so if you install two identical sized RAM modules on the same pair of ports, the system can alternate back and forth between the two, therefore doubling the speed at which it can be accessed and read from.
  4. kenglade thread starter macrumors 6502

    Dec 20, 2008
    So I can add 2 2.0's or two 4.0s. That makes sense. Many thanks
  5. Kingcodez macrumors 6502


    May 13, 2009
    If you can find what slot is channeled with what, then I think you could do 2x2gb and 2x4gb, and they would all work in DUAL channel mode, separately of course.
  6. kenglade thread starter macrumors 6502

    Dec 20, 2008
    Heck, I thought I was pretty good just to know where the slots were, much less the channels. I think I'll take the safe route: 4x2.0 and see how that works. So far it seems to be working pretty well on 2x2.0.

    Thanks, though.

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