RAM upgrade: 1x8 GB vs. 2x4 GB

Discussion in 'MacBook Pro' started by JTToft, Jul 11, 2012.

  1. JTToft macrumors 68040

    Apr 27, 2010
    Aarhus, Denmark
    Hello all.

    I am looking to upgrade the RAM on my MacBook Pro (see signature) from 4 GB to 8 GB, and I wanted to get your advice on it.

    I am looking at Corsair Vengeance 1600 MHz RAM and have the option of getting either two 4 GB modules or one 8 GB module. Since the price difference is negligible (about 8 USD - 10 %), I thought I'd go for the single module, making it significantly cheaper to upgrade to 16 GB at a later time.

    What I want to know is:
    Is the speed difference big enough that I should go for the two 4 GB modules? Or is there another compelling reason to choose the two 4 GB modules over the single 8 GB module?

    The specifications on the two options are as follows:
    2 x 4 GB (part no. CMSX8GX3M2A1600C9): CL9 9-9-9-24
    1 x 8 GB (part no. CMSX8GX3M1A1600C10): CL10 10-10-10-27

    - Thanks!
  2. GoreVidal macrumors 6502a


    Jun 19, 2011
    If the price difference is negligible, why on earth wouldn't you go for the 1x8GB? That way you only have to worry about buying another 1x8GB stick to go to 16GB later instead of having to ditch the 2x4GB and having to buy 2x8GB. It's a pretty simple decision.
  3. Mr MM macrumors 65816

    Mr MM

    Jun 29, 2011
    I would go for the 1x 8gb module as well.

    It would be best to upgrade at some later date to 16gb if the need arises. Also you could put the 2gb module that already came with your mbp.
  4. FastEddiebags macrumors 6502

    Jun 1, 2012
    agreed. Its the smarter choice since you wont be wasting your purchase if you decide to upgrade again.
  5. theBostonian Suspended

    Apr 15, 2012
  6. weemanpow3 macrumors 6502


    Mar 14, 2008
    If your looking for performance, stick with 2 x 4 GB so you can benefit from dual-channel. Dual channel is like a two lane highway so more traffic can get through faster instead of a congested single lane.

    I would stick with 2 x 4 GB. Ram is gonna be cheap regardless in the future.
  7. GoreVidal macrumors 6502a


    Jun 19, 2011
    Disagree. If the OP is even asking the original question, they will NEVER notice any performance gains in dual-channel RAM. They should just bite the bullet now and spend the $90 on 2x8GB and call it a day.
  8. dusk007 macrumors 68040


    Dec 5, 2009
    If you run a 13" MBP with only the HD 4000 I would go dual channel. Otherwise half the bandwidth usually isn't so bad for most normal applications.
    Effectively you have only one 64 bit Bus to the memory instead of 2x 64= 128bit.
    But the memory that the cpu needs for a workload would need to be evenly spread on both moduls for DC to work properly anyway. Usually DC helps a lot when many cores are accessing at the same time and GPUs. GPUs need lots of bandwidth. CPUs store so much in Caches that bandwidth doesn't really matter. A CPU cares about Latency more than Bandwidth.
  9. themumu macrumors 6502a


    Feb 13, 2011
    The benefits of dual (and triple) channel memory only really show up when you're dealing with some high performance applications, running commercial servers, etc. Most likely, if you have to ask, you will not see the difference.
  10. JTToft thread starter macrumors 68040

    Apr 27, 2010
    Aarhus, Denmark
    - Yes, my thoughts exactly. I just wanted to make sure about the difference in performance. I guess my need is mostly for more RAM rather than for faster RAM, so it probably doesn't matter.
    Perhaps I should save some money and go with 1333 MHz instead...

    Thanks all.
  11. iMacFarlane macrumors 65816


    Apr 5, 2012
    Adrift in a sea of possibilities
    I would NOT go for the 1333MHz RAM. Think about it. The main reason you want more RAM in the first place is for a performance boost. The boost will only be noticable when performing memory-intensive tasks which would otherwise overwhelm your 4GB of memory causing virtual RAM or swapfiles to cover the inequity. This will happen occasionally, more often depending on what you are doing.

    But, if you opt for 1333MHz RAM, and your computer now has 1600MHz RAM in it, aren't you opting for an immediate 20% reduction in memory speed for every byte your system addresses to memory?

    If even pairing is no longer an issue, why not upgrade one of your 2GB sticks up to 8GB, giving you a total of 10GB on board? Then you'd get the dual-channel performance for the first 4GB of memory being written (like you are now), and a drop to single channel when you dip into the remaining 6GB on the new stick. All of that will be written to your speedy RAM instead of the HDD/SSD (swapfile).

    Upgrade second stick to 8GB later when you wish. Win/win.
  12. Freyqq macrumors 601

    Dec 13, 2004
    Getting 1x8 is fine, but I recommend getting the exact same model ram if you upgrade later
  13. definitive macrumors 68000


    Aug 4, 2008
    with 1x8 you have the room to upgrade to 16 gigs in the future without having to dump your old ram, and i also think that a single stick might consume less power than two, which would save on battery life.
  14. lixuelai macrumors 6502a

    Oct 29, 2008
    You can run 1x8GB + 1x2GB. So you get 4GB of dual channel and 6GB of single channel. Intel calls this "Flex Memory".
  15. JTToft thread starter macrumors 68040

    Apr 27, 2010
    Aarhus, Denmark
    - I realize I didn't mention this, but I am currently using 1333 MHz RAM (standard from Apple), so no, I wouldn't lose any performance.
    You are right, though, that it would be silly to choose 1333 MHz if I were using 1600 MHz now.

    - That sounds like a good plan. I think I'll do that.
    The question is whether I should choose the 1600 MHz or not - I might be fine with the slower (and much cheaper) 1333 MHz.
  16. mac mac mac macrumors regular

    Oct 8, 2008
    Bellevue, WA
    I just ordered the 2012 MBP 15" base model. I understand that I can either replace both 2GB chips with 2 4GB chips to take advantage of dual channel memory, or buy 1 8GB chip to replace just one of the 2GB chip to get 10GB. The first 4GB is still dual channel.

    So which option would be better for my use? I plan to use it with Photoshop CS6, Illustrator, Keynote, Final Cut Pro X. It's a work laptop to help us make advertising materials. Will these more advanced applications better off to utilize all 8GB of DC memory, or more ram but only 4GB of that is DC? Just like the OP mentioned, the price between 2 4GB chips or 1 8GB chip is indifference ($47 vs $50 via Newegg). I'd like to just go with 16GB of ram, but it's a company laptop so I don't want to overspend. The company already dropped $1659 for this laptop :eek: This is our first Mac at work :D

  17. TickleMeElmo macrumors regular

    Jun 19, 2012
    Use your computer for a week with your normal workload and if you get pageouts then spend money on the RAM.
  18. SDAVE macrumors 68040


    Jun 16, 2007
  19. szolr macrumors 6502

    Jul 27, 2011
    London, UK
  20. Stridder44 macrumors 68040


    Mar 24, 2003
    Maybe it's just me but I don't see the point in not getting 16GB. Even the best of them are only like ~$100, and I mean honestly if you're going to upgrade you might as well make it worth-while so you never need to do it again. Do it right the first time, know what I mean?

    For example: CORSAIR Vengeance 16GB (2 x 8) for $114 which is the most highly rated (and also most expensive)

    or even this: G.SKILL 16GB (2 x 8) for $99. Both are DDR3 1600
  21. TXCiclista macrumors newbie

    Jul 10, 2011
    Quick point of clarification here: while the difference in clock speed may be a 17% reduction, the actual impact on RAM performance is ~1-2%.
  22. FastEddiebags macrumors 6502

    Jun 1, 2012
    I'd have to agree with you. Is your time worth the extra money you put in so that you never have to think about RAM again. You invested a good amount already in getting a MBP, why not put the extra 100. Some people say don't spend more money than you need too, but also don't waste money getting a 2x4 and having to buy 2x8 when you need it.
  23. omgitscro macrumors 6502a


    Jul 12, 2008
    You're obviously playing with a limited budget.

    Don't get 1600MHz unless you really need it. Any improvement in day-to-day use that ostensibly comes from dual-channel or the small clock speed difference between 1333MHz and 1600MHz is going to be psychological.

    1333MHz, 1x8GB is more than enough.

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