19dean66

Q: can i mix 4gb and 8gb off ram together on the imac 27 inch late 2013

can i mix 4gb and 8gb off ram together on the imac 27 inch late 2013 because when i got my imac a few weeks ago it only comes with 8gb 2x4 and if i buy 16gb 2x8 can i slot them in with the 2x4gb to make a total off 24gb can someone tell me please

iMac, OS X Mountain Lion (10.8.5)

Posted on Dec 4, 2013 8:35 AM

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Q: can i mix 4gb and 8gb off ram together on the imac 27 inch late 2013

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  • by DavidW909,

    DavidW909 DavidW909 May 1, 2015 3:35 AM in response to 19dean66
    Level 1 (0 points)
    May 1, 2015 3:35 AM in response to 19dean66

    In a late 2013 27" iMac, Will i receive a proportional improvement in performance if upping my ram to 24 (4g and 8g and 4g and 8g) in the appropriate slots as opposed to increasing the total ram to 32 by replacing the 2 original 4g cards with 4 x 8g cards?  I.e., will 32g of ram result in such a significant improvement that a 24 g config. is sort of a waste?

     

    ideally i would like to make use of the 2 original 4g cards, hence the 24g option being considered.

     

    thanks

  • by mquiz,

    mquiz mquiz May 24, 2016 9:53 AM in response to DavidW909
    Level 1 (8 points)
    iPad
    May 24, 2016 9:53 AM in response to DavidW909

    Why is best to install DIMMs in pairs

    I am going to add a 8GB DIMMs to the 2*4GB originally in my Imac 27i retina 5K 3;3 GHZ late 2015

  • by Kurt Lang,

    Kurt Lang Kurt Lang May 24, 2016 10:12 AM in response to mquiz
    Level 8 (37,815 points)
    Mac OS X
    May 24, 2016 10:12 AM in response to mquiz

    It depends on how the architecture of the board is laid out, and how the memory controller is designed to access those slots. As an example, let's say a memory path is 128 bits. On one Mac, a single slot may be a full 128 bit path, but on another, you have to fill two slots (each with a 64 bit stick) to achieve the full 128 bit path. In such a case, the latter will work with only one slot filled, but the data flow will always be cut in half, essentially slowing down any processing using that truncated path.

  • by mquiz,

    mquiz mquiz May 24, 2016 11:52 PM in response to Kurt Lang
    Level 1 (8 points)
    iPad
    May 24, 2016 11:52 PM in response to Kurt Lang

    Does this mean that my mac could get slower after the upgrade than it was before ?

    Or could the perf improvement be only negligible ?

    For 35€ I can get a 2nd 8GB ... worth the investment, I guess

  • by BobHarris,

    BobHarris BobHarris May 25, 2016 6:20 AM in response to mquiz
    Level 6 (19,410 points)
    Mac OS X
    May 25, 2016 6:20 AM in response to mquiz

    mquiz wrote:

     

    Does this mean that my mac could get slower after the upgrade than it was before ?

    Or could the perf improvement be only negligible ?

    For 35€ I can get a 2nd 8GB ... worth the investment, I guess

    Memory intensive operations will be slower.  Storage I/O and Network I/O intensive operations will not notice.

     

    If you can afford matched pairs of RAM, it would be better.  But if your Mac is currently doing lots of paging and swapping to disk, then more RAM, even if unmatched, would be an improvement.

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