RAM Upgrade 4+4+8 Gb in Imac - Possible?

Discussion in 'iMac' started by arunkumar786, Jan 15, 2016.

  1. arunkumar786 macrumors newbie

    Joined:
    Jan 15, 2016
    #1
    I have bought a new iMac 27 inch, and it has come with 2x4Gb RAM so 8Gb RAM, I want to upgrade it to 16 Gb RAM, is it possible that, only if i buy a single 8 gb ram and install it in the 3rd Rack will it work fine? or do i need to remove the previous installed RAM? and install a fresh 2x8Gb Ram? also suggest me which is better?
     
  2. theNatest macrumors member

    theNatest

    Joined:
    Jan 14, 2016
    Location:
    Twin Cities
    #2
    RAM should be installed in pairs. If you only want to go up to 16 gigs then buy 2x4gb. If you want a better pop go for 2x8gb adding to your stock apple ram for a total of 24gb. The price difference is minimal and worth the extra coins.

    I believe crucial RAM 2x8gb is around $85 and OWC $115 right now.

    For placement - I've read the best way to install the aftermarket RAM is in the slots that the current Apple RAM sits and slide the apple ram into the open slots - correct me if I'm wrong on that one.
     
  3. jazzer15 macrumors 6502

    Joined:
    Oct 8, 2010
    #3
    I'm not saying you are wrong because I don't know, but I wonder why this would matter. I picked up 2x8 and need to install it, so I'm curious of the answer.
     
  4. MadDane macrumors 6502a

    Joined:
    Apr 5, 2015
    #4
    AFAIK as long as the RAM is installed in pairs, you are good to go. I don't see, from a technical perspective, why using two slots would be better than the other two slots. The hardware doesn't care which of them you are using. I might be wrong, but that is how I see it based on my knowledge.
     
  5. arunkumar786 thread starter macrumors newbie

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    Jan 15, 2016
    #5
    Thank you all... But is there any technical reason that we should install RAM only in pairs...? Why can't we install a single RAM over the already installed 2 x 4GB RAM? Just curious to know.. That's all...
     
  6. florinbss2 macrumors newbie

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    Oct 30, 2015
    #6
    Because not working in dual channel and is at half speed
     
  7. Ainze macrumors regular

    Ainze

    Joined:
    Feb 28, 2010
    #7
    It gives a speed bump. But technically you don't have to. You just lose performance.

    In the case of 4 4 8, you could do it if you wanted. Just make sure you put the 4s in the right slots to pair them to make the best of the situation.
     
  8. arunkumar786 thread starter macrumors newbie

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    Jan 15, 2016
    #8
    You mean to say that, if i put 2 x 4gb then it should be in 1st and 2nd slot, and 1 x 8gb in 3rd slot... not the other way round, like 1 x 8gb in 1st slot and 2 x 4gb in 2nd and 3rd slot... correct me if i am wrong...
     
  9. Ainze macrumors regular

    Ainze

    Joined:
    Feb 28, 2010
    #9
    Yes, probably. Leave the memory that came with it in whichever slots they're already in. They will already be paired. And then stick your 8GB stick in any free slot.
     
  10. arunkumar786 thread starter macrumors newbie

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    Jan 15, 2016
    #10
    Thanks a lot! also can someone suggest which is the best brand that produces RAM for iMAC...
     
  11. Ainze macrumors regular

    Ainze

    Joined:
    Feb 28, 2010
    #11
    I always buy mine from Crucial. They'll even match the RAM to your Mac automatically (and they'll also recommend pairing). But other people may have better suggestions.
     
  12. zone23 macrumors 68000

    Joined:
    May 10, 2012
    #12
    I only install RAM in pairs, thats the way it should be done so thats how I do it. You loose performance other wise and I don't see why anyone wouldn't install it in pairs. Is the store too far? Do you live in a county where its hard to get? No Amazon? Why wouldn't you? Why would I want to cut the speed of the memory in half? You would be better off without the other stick (probably).
     
  13. arunkumar786 thread starter macrumors newbie

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    Jan 15, 2016
    #13
    Ya I Understand... and in my country we have all facility to get things... but since i had idea of having only 16 gb RAM , i thought why i should go for 2 x 8Gb where i already have a 2 x 4Gb... but after getting suggestion from most ppl, to put it in a pair , may be i will go and add 2 x 8 Gb RAM in my other 2 slots... So now my question is if i have 2x 4Gb in first 2 slots and 2 x 8Gb in the next 2 slots it works fine right?
     
  14. zone23 macrumors 68000

    Joined:
    May 10, 2012
    #14
    Personally if it were me and this may actually do nothing but I like having the larger RAM sticks in the first two slots or the slots were your RAM is in now.
     
  15. arunkumar786 thread starter macrumors newbie

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    Jan 15, 2016
    #15
    Fine!!! Great!!! thanks to all for solving my queries... also i didn't get the technical reason behind these kind of RAM installation ... if any one knows can share it little detailed...
     
  16. zone23 macrumors 68000

    Joined:
    May 10, 2012
    #16
    When running RAM in pairs it enables dual channel mode which is basically going form say 1 channel to 2 channels for data transfer between the RAM and your PCs main board. Obviously your RAM has many more than 1 or two channels but hopefully you get the idea. I wouldn't say the memory runs twice as fast but it something like that.. I'm no expert someone else can chime in with more detail if they want.
     
  17. Ainze macrumors regular

    Ainze

    Joined:
    Feb 28, 2010
    #17
    Memory interleaving allows you to avoid a bottleneck communicating to the RAM module. If you're trying to push data to the chip faster than it can support it, you can send some data to its partner instead. Now if you assume that you write to both chips simultaneously, almost in a one-for-you, one-for-me fashion, you see why the chips need to be laid out in a symmetrical manner. RAID hard drives, then optimised for speed, work on a roughly similar concept.

    As for your situation, if you really only want 16GB, you could just go for 2 more 4s. But if you want to put 2 8s in there, that will work fine too. That's what I have (24GB, 4-4-8-8) and it works a treat.
     

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