About 1.35v DDR3 RAM...

Discussion in 'MacBook Pro' started by bill-p, Dec 4, 2011.

  1. bill-p macrumors 68000

    Jul 23, 2011
    I just installed a pair of Crucial branded DDR3 RAM that they claim to be 1.35v.

    And it works. But how do I know if it's actually running at 1.35v or not? Or is that supported by the chipset at all?
  2. thundersteele macrumors 68030

    Oct 19, 2011
    A few weeks ago there was another thread where someone claimed that 1.35V RAM was working in his machine. However also in that case there was no way to verify if they were actually operating at 1.35V.

    You could try to run some benchmarks with old and new ram and compare the power usage. However it's quite difficult, since the ram only uses a small amount of energy compared to the rest of the machine.
  3. Steve's Barber macrumors 6502a

    Jul 5, 2011
    Exactly *what* did you install the RAM in?

    MBP13 takes 1.35v chips so if that's what you did then of course it will work. The larger MBP models want 1.5v.
  4. thundersteele macrumors 68030

    Oct 19, 2011
    I don't think that's correct. All current MBPs accept the same RAM.

    Low voltage DDR3L RAM runs both with 1.35 v and 1.5 v, so you can use it in any MBP. It will run in 1.5v mode if the RAM slots don't support low voltage ram, or if it is paired with 1.5v RAM.
    The question is whether it will run in 1.35v mode or in 1.5v mode in the MBP, and how this can be checked.
  5. bill-p thread starter macrumors 68000

    Jul 23, 2011
    An Early 2011 15" MBP.

    I'm not aware of the fact that the MBP13 takes 1.35v chips. Is there more information on this?

    Also, why wouldn't the 15" and 17" be able to take advantage of 1.35v chips? It makes no sense to me.

    As for those asking for the difference, I do notice a drop in surface temperature around the palm rest area. I use AutoCAD, Photoshop, and such applications that push the machine quite hard, so this drop in surface temperature is actually quite noticeable. I didn't use iStat to record temperature prior to the replacement, so I don't exactly have concrete numbers to back things up, but there is a noticeable difference.

    Then again, it might also be because the 1.35v move is also an update from 4GB original to 8GB, and thus less hard drive swapping for the mentioned applications.
  6. dusk007 macrumors 68040


    Dec 5, 2009
    If the 13" CPUs manage eat 1.35V the 15/17" will do too.
    They run effectively the same IMC whatever one supports the other does too.
    I don't know of any official facts. Officially Intel will support DDR3L with Ivy Bridge but on Desktop Motherboards 1.35V used to work fine even with Clarkdale CPUs which are the same as the 2010 15" MBP Arrendale CPUs.

    In any case did anybody try reading out voltages in Windows with AIDA64 or just CPUz. I don't want to restart to Windows and a VM is no use for this but part of the SPD settings is the running voltage.
  7. bill-p thread starter macrumors 68000

    Jul 23, 2011
    Well, the funny thing is... CPU-Z shows 1.28v, so I'm not sure if it's reporting correct SPD.

    Here. Please see attachment.

    Attached Files:

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  8. thundersteele macrumors 68030

    Oct 19, 2011
    1.28v is within the range that the low voltage RAM accepts I think.

    You could go all the way and put back in the old RAM and read out the voltage again. I would be very interested to see it!
  9. Adamantoise macrumors 6502a

    Aug 1, 2011
    Only God knows why you guys care what voltage is being applied across your RAM.

    Honestly, someone explain to me how this is something any consumer (even the discerning ones) should concern him or herself with.
  10. thundersteele macrumors 68030

    Oct 19, 2011
    about 10% less energy consumed by the memory, or about 2% savings on the full machine. That's about 8-10 minutes longer battery duration.

    Also, it's just nice to have something new and bleeding edge.
  11. dusk007 macrumors 68040


    Dec 5, 2009
    1.28 doesn't sound like it is off by too much.
    Most of those low voltage ram have a 1.35V setting for 1600Mhz but 1.25V below.

    I upgraded too but on the 2010 it stays at 1.5V. Cost difference was 2€ so I thought I'll give it a try.

    It is about a 2-4% power savings in total on an idle machine but under load it means 3 Watts less. If the stuff cost almost the same why not.
    Gets you more real world benefit than some ridiculously expensive performance upgrades for almost no extra money.
  12. bill-p thread starter macrumors 68000

    Jul 23, 2011
    Put back in old RAM yesterday and CPU-Z showed 1.5v.

    But I also found that CPU-Z is only reading SPD directly off the RAM chip, not the actual voltage. AIDA64 or Everest don't really show voltage information at all.

    Considering battery run time, among other things, I'm inclined to say at least that my battery life improved going from 4GB 1.5v to 8GB 1.35v. It used to say 7:40 in battery meter, but now it says 8:50 more consistently.

    Also my usage often shows 2GB free in Activity Monitor with 8GB installed for those wondering.
  13. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    That's not how it works. The 2011 models will run with both 1.5 volt and 1.35 volt DDR3 RAM as long as the other specs are correct. 1.35 V ram will run slightly cooler and, in theory, extend your battery life. The actual differences are difficult to quantify. Google has plenty of info on DDR 3 1.5 and 1.35 ram. Wikipedia is a good place to start.
  14. imperialnavy macrumors regular

    Jul 22, 2009
    Which ram are we talking about here ? The one by Adata ?
    Last time i used those in my early 15inch MBP, it ran at 1333Mhz 1.5V....
    Maybe because it didnt support Plug and Play ?

    I sent it back to Amazon and will go for Kingston 1600Mhz now...
  15. bill-p thread starter macrumors 68000

    Jul 23, 2011
    I got mine directly from Crucial. Was waiting for Amazon, Newegg and other outlets to get them first and probably shave off a few dollars, but I just couldn't resist it. Plus dealing with Crucial directly has been less of a hassle for me.

    Here's a link to the product page:

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