Question about Ram

Discussion in 'MacBook Pro' started by Macsta, Dec 7, 2011.

  1. Macsta macrumors member


    Feb 27, 2008
    Hi all,
    I have a late 2011 13" MacBook Pro base 2.4 i5 4g 500g. I am thinking of upgrading to 8 gigs of ram. Question when I go to Crucial's ram config they recommend:

    DDR3 PC3-10600 • CL=9 • Unbuffered • NON-ECC • DDR3-1333 • 1.35V

    When I go to G-Skill they recommend:

    DDR3 PC3-10666 • CL=9 • Unbuffered • NON-ECC • DDR3-1333 • 1.5V

    What is the difference between 10600 vs 10666 and 1.35V vs 1.5V?

    Which is better and which one should I get? There is only a $10 difference between the two

    Thanks in advance
  2. some idiot macrumors member

    Oct 12, 2011
    I may be wrong, but the 10666 seems like it could be a slightly overclocked model.
  3. appleraj macrumors member

    Jul 17, 2011
    Applicable models
    MacBook Pro (13-inch, Early 2011)

    Memory specifications
    These MacBook Pro models have these memory specifications:

    Number of memory slots 2
    Base memory 4 GB
    Maximum memory 8 GB
    Memory card specifications - Double Data Rate Small Outline Dual Inline Memory Module (DDR3) format
    - 67.6mm x 30mm (1.18 inch)
    - 2 GB or 4 GB
    - 204-pin
    - PC3-10600 DDR3 1333 MHz type RAM
    Additional notes For best performance, fill both memory slots, installing an equal memory module in each slot.
  4. VMMan macrumors 6502a

    Mar 29, 2009
    10600 and 10660 are the same. They have been rounded using different standards, AFAIK.

    I didn't think our MBPs supported 1.35V?

    I suppose you could get the dual 1.35V/1.5V if you get a comp later that supports 1.35V?
  5. thundersteele macrumors 68030

    Oct 19, 2011
    I think the PC3 number is 8x the MHz, which would be 8 x 1333 = 10664. Some vendors brand it as PC3-10600, others as PC3-10660, and I've also seen it as PC3-10666. It's all the same.

    Now there is a difference between 1.35v and 1.5v RAM. Both should work in the MBP, but it's not clear that the 1.35 will really run at the lower voltage, so there might be no real benefit from choosing that one.
  6. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    The first number is the theoretical max data transfer rate in mega bytes per second. Both will work but in theory the gskill will be faster. This number has become marketing jargon so it's ok to ignore it.

    The second number is the voltage at which memory runs. In theory the lower voltage memory should run cooler (and be easier to overclock) but back in the real world there are no quantifiable differences. Sandy bridge specifies 1.5 V but both will work.

    The important number is the clock frequency (1333). Even though apple does not say so the sandy bridge MBP will happily run with DDR3 1600 and 1866 memory. It is a bit more expensive but the small difference in performance can actually be observed in benchmarks.
  7. thundersteele macrumors 68030

    Oct 19, 2011
    From Wikipedia:
    I also made a mistake earlier, it is 8x1333(1/3) = 10666(2/3). There is no difference here between the two products, not even in theory.


    The intel websites lists 1066 and 1333 for the 2.2 GHz sandy bridge (2675QM) and 1066/1333/1866 for the 2.4/2.5 GHz CPUs (2760QM and 2860QM). Are you saying that this information is also inaccurate? Or will the memory just down clock?
  8. shootist macrumors regular

    Dec 8, 2011
    If you read the Crucial questions and answers for that RAM this question has been asked and answered a few times.
    The answer is the Macbook Pro late 2011 13" will take either the 1.35V or the 1.5V RAM. The difference is the 1.35V RAM will use less power, and I would suspect produce less heat.

    If you expand the Crucial Suggested RAM you will see they also offer 1.5V RAM.

    I can confirm this as I installed the 8GB 1.35V kit into the Macbook Pro I bought on Black Friday and it worked without any problems.

    And Crucial has tested the late 2011 MBP models and they do support 16GBs of RAM. Although the manual states the Max RAM you can install is 8GBs.

    I asked the 16GB question myself and got the above answer.

    Now the question is do you buy the 1.35V 8GB kit for 46+ dollars or Max out the RAM at a cost of close to $400.
  9. Macsta thread starter macrumors member


    Feb 27, 2008
    Thanks everyone for the replies

    I ended up going with the G-Skill not for any performance gains but it got better reviews and less DOAs then the Crucial
  10. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    First point. Yes, you're quite right. I had always assumed it was marketing jargon vs the calculation and I didn't realise it was a rounding game.

    Second point. I am pretty sure that it's only up to 1600 for the 2.4 and 2.5 mobile chips. What actually happens is it all depends on what memory the motherboard supports (and I cannot tell you what it is for apple motherboards). Most motherboards support higher frequency ram than the CPU. So if you use 1600 MHz memory and the mb supports it, then it will run at 1600. This quickly becomes a very complicated discussion and I slept through those computer science lectures. :(
  11. Ice Dragon macrumors 6502a

    Ice Dragon

    Jun 16, 2009
    It will be pushed down to 1333MHz though still support the 1600MHz. Make sense?
  12. shootist macrumors regular

    Dec 8, 2011
    Funny but I've had problems with G-Skill and never had problems with Crucial (Micron) or Kingston.

    the one time a friend had problems with Crucial memory was in his desktop that was inside a cabinet with the door closed, he also had problems with failing hard drives. Heat related.
    Crucial replaced the memory 4 years after it was purchased, No questions asked.
  13. thundersteele macrumors 68030

    Oct 19, 2011
    Ok, this makes sense... although it's also really confusing... if the CPU supports 1333 and the MB supports 1600, then the RAM runs at 1600... what happens to the CPU? Does it explode :D

    Does anyone have experience with Samsung RAM? It's the cheapest brand name RAM available in my local microcenter (not a big fan of mail-in-rebates and online shopping). The reviews on amazon seem quite good.

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