New iMac 5K RAM upgradable?

Discussion in 'iMac' started by netdudeuk, May 24, 2015.

  1. netdudeuk macrumors newbie

    Joined:
    Nov 27, 2012
    #1
    Hi

    Does anyone know if this is upgradable with the same slot near the power jack ?

    Is there a simple definitive statement regarding what is needed for it to take it up to 16GB .

    Thanks
     
  2. aevan macrumors 68000

    aevan

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    Location:
    Serbia
    #2
    A quick visit to the official iMac 5K specs page says that both the low-end and the high-end iMac models (like all 27" iMacs) have user accessible RAM slots, so yes, the RAM is upgradeable.

    http://www.apple.com/imac-with-retina/specs/

    It needs to be 1600Mhz, unbuffered, nonparity, 204-pin. It's not mentioned, but it should also be low-voltage (1.35V or supporting both 1.35V and 1.5V)
    You can easily order this from a lot of RAM manufacturers.
    You can combine it with the RAM already installed on your Mac or replace it completely for 16, 24 or 32Gb RAM.

    https://support.apple.com/en-us/HT1423
     
  3. andy9l macrumors 68000

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    England, UK
    #3
  4. netdudeuk thread starter macrumors newbie

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    Nov 27, 2012
  5. loekf macrumors 6502

    loekf

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    Mar 23, 2015
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    Nijmegen, The Netherlands
    #5
    Note it has to be SO-DIMMs, DDR3, PC12800 (= 1600 MHz x 2 x 4 bytes per clock), CL11.

    You could try shorter CAS latency (e.g. CL9) and faster clocks (e.g. 1866 MHz), but no guarantees.


    Besides Crucial, Corsair is also selling "Mac qualified RAM".
     
  6. stevieraveon macrumors newbie

    Joined:
    Dec 16, 2012
    #6
    I just got a new iMac 5k two days ago. Yesterday I walked into MicroCenter and bought 32 GB of memory for under $200. Price tag shows $144.99, but MicroCenter had a sale for $99.

    The whole process to upgrade took literally 2 minutes.
     

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  7. parkp81 macrumors member

    Joined:
    Jul 6, 2010
    #7
    I looked up the one you purchased at it says its "CL9". I see the one for $129 which is "CL11". But the post from "loekf", says it should be CL11, but how's it working for you?
     
  8. loekf macrumors 6502

    loekf

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    #8
    this is the kit you normally find on the Crucial website:

    http://eu.crucial.com/eur/en/imac-(retina-5k,-27-inch,-late-2014)/CT6313719

    I have two of these in my 5k iMac.

    Looks like you have this one:

    http://eu.crucial.com/eur/en/ct2c8g3s1339mceu#reviewDetails

    which is CL9.

    I think Apple's official specs are CL11. CL9 *could* give you a 1-2% performance gain for some tasks, but no guarantees. The higher the clock speeds for memory these days, the less relevant CAS latency is.

    You also have to careful if you add faster (CL10, CL9) RAM to the two already placed modules by Apple, which are CL11. Your iMac might decide to downgrade your RAM (e.g. to 1333 MHz).
     
  9. parkp81 macrumors member

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    Jul 6, 2010
    #9
    I bought the one from Amazon that is the CL11 version after using the Crucial website to determine which memory was compatible. So far it has been working great, ran a few memory tests and it passed all. No crashes or waking up from sleep issues I've read about as well. I almost bought the CL9 from Microcenter before, because I noticed it was priced lower, but now glad I did not.
     
  10. ZipZap macrumors 601

    Joined:
    Dec 14, 2007
    #10
    So the ones at Amazon do not match the part number that Crucial says:
    CT6313736
    As posted elsewhere, my sleep wake feature does not work and its been linked to the Amazon chips.

    Has anyone used the correct chips?
     
  11. dnoph macrumors member

    Joined:
    Apr 1, 2015
    #11
    Does the RAM have to match? For example, if theres 4 slots, can I put in a 2GB, 4GB, and an 8GB?

    Are there any issues using different sized RAM?
     
  12. loekf macrumors 6502

    loekf

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    #12
    I have two CT6313719 kits (so 4 x 8 GB) in my 5k iMac. Works great. I can't find the number you mentioned on Crucial's website, but on Amazon.com I can. This kit can be found when you use the search tool on Crucial's website. The specs for this other kit on Amazon.com looks similar (1.35 V PC12800 1600 MHz SO-DIMM CL11).
     
  13. loekf macrumors 6502

    loekf

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    #13
    You have to take into account that Intel CPUs (and AMD's as well) prefers to access two memory slots in parallel (interleaving). Suppose if you have 4 slots, let's say A, B, C and D. If you put a 2 GB in A, a 4 GB in B and 8 GB in C.. the CPU will access the banks indivually and you at least will get a performance hit.

    It's preferred to have the same size, manufacturer in two slots next to each other, so e.g:

    A - 4 GB (Apple puts it here by default)
    B - 4 GB (Apple puts it here by default)
    C - 8 GB (brand XX)
    D - 8 GB (brand XX)
     
  14. Notechy macrumors member

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    Apr 11, 2015
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    Surrey
    #14
    But is it ok to fill just 3 slots, say 3x8GB?
     
  15. loekf macrumors 6502

    loekf

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    #15
    You also will get a performance hit, of 5-10%, because memory is not accessed via interleaving (also called dual-channel). Not sure how the memory controller works, but maybe the two upper slots (where Apple puts the two 4 GB modules by default) are accessed interleaved and the single 8 GB module is accessed in a single-channel way.

    You will get a hit depending on where the memory is mapped in the address space.
     
  16. ZipZap macrumors 601

    Joined:
    Dec 14, 2007
    #16
    Does your sleep function work. These chips from amazon cause issues whereby my unit sleeps and never wakes up.
     
  17. ZipZap macrumors 601

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    Dec 14, 2007
    #17
    The answer is no. You need to install in pairs.
     
  18. AlexJoda macrumors regular

    AlexJoda

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    Apr 8, 2015
    #18
  19. loekf macrumors 6502

    loekf

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    #19
    Actually never use sleep mode. I think in screen lock mode with no processes active and the screen disabled, the CPU stays active.
     
  20. phpmaven macrumors 68040

    phpmaven

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    #20
  21. ZipZap macrumors 601

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    #21
  22. john0011 macrumors member

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    May 30, 2015
    #22
    Those of you who went with a lower CL upgrade stick, did you remove the apple memory in slot a and out the lower CL stick there? I assume slot A is closest to the CPU (would be used first).
     
  23. ZipZap macrumors 601

    Joined:
    Dec 14, 2007
    #23
    Lets be clear, the reports of wake issues are from people who bought CL11. You should not really use memory not designed for your device.

    For me, I also don't want added memory to cause any hardware issue. I was at the Crucial site and there are many threads about this wake problem. Each time, Crucial acts like its news to them wiling, of course to exchange, but not willing to figure out whats going on. Posts back to the beginning of the year.

    One poster indicated that the problem may be, that Apple memory chips (Samsung I believe) don't behave well with other chips.
     

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