1.35 V & 1.5 V RAM for late 2013 iMac's

Discussion in 'iMac' started by jobinho, Oct 14, 2013.

  1. jobinho macrumors newbie

    Joined:
    Oct 12, 2013
    #1
    From what i've researched iMac's can handle both 1.35 V & 1.5 V RAM.

    I'd like to know if either voltages is a better option for the Haswell iMac's.

    Could adding 1.5 V potentially harm the computer or is 1.35 V more of a power saving measure?

    My hunch is the 1.5 V in an iMac would be fine and 1.35 V would optimise a MBP.

    I had ordered Kingston HyperX Plug & Play 1.5V http://www.amazon.co.uk/gp/product/B008H7IGGI/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1 due to it's low latency but know of a more expensive 1.35 V version. I'm wondering whether it's worth getting a lower voltage module set to optimise my computers lifespan.

    Any advice or opinion would be really helpful. ;)
     
  2. Bear macrumors G3

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    #2
    Lower voltage also translate into less heat generated. There's also a good chance the memory slots are only wired for the lower voltage.

    Getting memory with a different CAS Latency than what is supported has a chance of not working or causing sporadic errors.

    In this case I would definitely get memory at the supported voltage and would probably just stick with the supported CL.
     
  3. Chippy99 macrumors 6502a

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    Apr 28, 2012
    #3
    I'd say there is ZERO chance of that, Bear. Haswell CPU's support 1.35 and 1.5v memory and Apple would have to try very hard to make 1.5v be a problem. Plus, they know that countless millions will install 3rd party ram and many of those millions will install 1.5v ram. Apple really don't want millions of RMA's and/or repairs to deal with, do they.

    However, I agree with your recommendation to stick with the correct CAS and that 1.35v is the preferred option.
     
  4. Bear macrumors G3

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    #4
    I'd say hard wired for a specific voltage is a possibility. It has happened before.
     
  5. Sam Spade macrumors regular

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    Aug 30, 2007
    #5
  6. Jaguarxl, Oct 14, 2013
    Last edited: Oct 14, 2013

    Jaguarxl macrumors member

    Jaguarxl

    Joined:
    Nov 29, 2012
    Location:
    Brazil
    #6
    I just ordered the new iMac with 8Gb RAM, because I´m planing to upgrade with cheaper memory modules. (Apple charges to much).
    Doing some research, I found out the ideal is to buy memory modules with same CL as Apple originals (CL11). That´s if you plan to use together with original ones. Becouse different CL will make your imac run as it was 1333Mhz, not 1600Mhz, even if both modules are 1600MHz. Becouse the system tends to use the lower speed.
    Correct if I´m wrong plz! But that was I found out researching over the internet for the best setup!:D
    That´s ideal memory module I found:
    Crucial CT2C8G3S160BM, 16GB Kit (8GBx2) DDR3 1600 MHz (PC3-12800) CL11 SODIMM 204-Pin 1.35V/1.5V
    http://amzn.com/B008LTBJFW
     
  7. RedReplicant macrumors 6502a

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    Mar 31, 2010
    #7
    So, as per JEDEC DDR3L standard the 1.35V modules must be backward compatible to JEDEC DDR3 1.5V standards. Meaning 1.35V modules will be fine for a 1.5V application. This would lead me to believe that most memory companies are producing 1.35V modules by default to cut down on supply chain costs as they can produce 1.35V modules and sell them as 1.5V modules for marketing purposes. Haswell wants 1.35V.
     
  8. jobinho thread starter macrumors newbie

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    Oct 12, 2013
    #8
    Im sure i've read somewhere that the new iMacs ship with 1.5 V cl11 RAM. Would seem strange to advise against using 1.5 V if that were the case.

    Can anyone verify this?
     
  9. Sam Spade macrumors regular

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    Aug 30, 2007
    #9
    Both Crucial and OWC claim the Late 2013 Haswell iMac is 1.35 V.
     
  10. RedReplicant macrumors 6502a

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    Mar 31, 2010
    #10
    Well, if you look at the huge version of the iFixit teardown - http://d3nevzfk7ii3be.cloudfront.net/igi/5fBMe5VFakfvXcOJ.huge - we get PC3L-12800S-11-12-B4.

    The L means it is DDR3L ram - which is 1.35V.
     
  11. drambuie macrumors 6502a

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    Feb 16, 2010
    #11
    According to the Intel 4th generation CPU datasheet, memory interface voltages are as follows- direct quote:

    DDR3/DDR3L I/O Voltage of 1.5 V for Desktop

    The i7 4770k used in the 3.5GHz iMac can use 240 pin DIMMs at up to 1.65v, which is recommended for memory speeds between 2000 and 3000MHz.

    The Haswell name is no longer used by Intel. They are now referred to as ARK CPUs
     
  12. RedReplicant macrumors 6502a

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    Mar 31, 2010
    #12
    No iMac has a K cpu stock - the 3.5GHz iMac has an i7-4771.
    The RAM speeds (2000-3000MHz) and voltage (1.65v) listed there are for overclocking purposes.
    The official Haswell name is "4th Generation Intel Core Processor Family", not ARK.
    ARK is simply Intel's online product catalog.
     
  13. Giuly, Oct 14, 2013
    Last edited: Nov 23, 2014

    Giuly macrumors 68040

    Giuly

    #13
    [​IMG]

    Good thing that the JEDEC specifications make everything down to CL9 at 1600MHz mandatory.

    What could cause trouble is 1866MHz RAM, but even that one ran fine on 2011 Macs already. However, the price for RAM is skyrocketing, and the 16GB 1866MHz Kingston HyperX Plug'n'Play kit is no exception.
     
  14. RedReplicant macrumors 6502a

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  15. NeoCracer macrumors member

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    Jun 29, 2009
    #15
    I have installed an extra 16GB in my new iMac, totaling in 32GB of ram.
    I have put in Corsair Vengeance ram, and they are 1.5V.

    So far I have no problems whatsoever and the iMac doesn't get hot at all. It's really great, the computer stays so cold!
     
  16. Chippy99 macrumors 6502a

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    Apr 28, 2012
    #16
    I don't know where it has happened before Bear. Do you mean with Apple?

    Apple is such a huge company (obviously), it would be suicide for them to design the motherboard such that it would not work with 1.5v ram. The number of RMA's would run into the 1000's. And for what benefit? Makes no sense at all.

    Personally I rule this out 100%. 1.5v ram will work fine, I am positive of it. And by way of anecdotal evidence, the 2012 iMac also ships with 1.35v, but countless thousands of people run 3rd party 1.5v memory without issues. Me, for one ;-)
     
  17. elithrar macrumors 6502

    elithrar

    Joined:
    May 31, 2007
    #17
    Which specific Vengeance model? This 1600MHz CL9 model? I'm asking as I'm about to buy a couple of sticks given that it's the only decent stuff in my local area.
     
  18. jobinho thread starter macrumors newbie

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    Oct 12, 2013
    #18
    So today I decided to call Apple care and they told me (after speaking to 2 dumb-asses) that I should use 1.35 cl11 RAM as it would optimise the longevity of my machine.

    I've returned my Kingston HyperX and have ordered Crucial, I can forgo the 2% in memory speed anyway. Im sure all of you with 1.5/cl9 will be fine by the way, just my OCD risk limitation kicking in before I receive my rip-off computer.
     
  19. elithrar macrumors 6502

    elithrar

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    May 31, 2007
    #19
    Not true, but I can't blame them for sticking to the book: say the wrong thing and customers go crazy.
     
  20. Sam Spade macrumors regular

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    Aug 30, 2007
    #20
    What problems would 1.35V CL9 cause? As noted, Apple recommends CL11...
     
  21. elithrar macrumors 6502

    elithrar

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    May 31, 2007
    #21
    None. As stated upthread, 1.35V DIMMS can run at 1.5V. CL9 DIMMS are (effectively imperceptibly) faster, but can/will run at CL11 in a mixed environment.

    There is no "danger" to having 2x 4GB 1.35V CL11 DIMMS and 2x 4GB "1.5V" CL9 DIMMS, although you'll find that most DDR3-1600 SODIMMS are 1.35V baseline.
     
  22. Chippy99 macrumors 6502a

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    Apr 28, 2012
    #22
    What you say seems logical (and its what I originally thought too) but it's not correct.

    With the 2012 iMac (and I assume therefore also the 2013), if you mix memory types what happens is the iMac will run the memory at the fastest CAS timings (i.e. lowest CL number) and will clock the memory bus at whatever frequency the slowest stick can manage at those fast CL timings. This may seem odd, but it is what happens.

    So what does this mean? Well for example suppose you have 8GB of Apple factory ram installed running CL11 @1600MHz and you add another 8GB of (say) Corsair 1600MHz CL10 memory. Instead of running at 1600MHz, CL11 - which is what you might expect to happen - in fact what happens is it runs at 1333MHz, CL10.

    So it is important when mixing memory that you bear this in mind. If you add 1600 CL9 memory, you will actually make your system slower than if you add the (much cheaper) 1600 CL11 memory!

    Of course if you are going to replace your Apple memory and only install fast memory, then none of the above applies.
     
  23. LuckyDuck69 macrumors newbie

    Joined:
    Oct 16, 2013
    #23
    This. I used the following product and did the same thing. No issues at all.

    http://www.newegg.com/Product/Product.aspx?Item=N82E16820233598
     
  24. roland.g macrumors 603

    roland.g

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    Apr 11, 2005
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    One mile up and soaring
    #24
    Is there a difference between that and this -> http://www.crucial.com/store/mpartspecs.aspx?mtbpoid=81CE351CA5CA7304

    Other than price.
     
  25. NeoCracer macrumors member

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    Jun 29, 2009
    #25
    I have bought the Corsair Vengeance 16GB (2x8GB) DDR3 1600 MHz (PC3 12800) (CMSX16GX3M2A1600C10) to be precise.
     

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