8 GB + 2 GB Ram in 2012 non-retina MBP

Discussion in 'MacBook Pro' started by liya1201, Jul 13, 2012.

  1. liya1201 macrumors member

    Joined:
    Sep 8, 2010
    #1
    I will order a low-end 2012 4 GB ram (2 GBx2) 15-inch MBP non-retina soon and just wondering if anybody has tried to only replace one 2 GB Apple's ram with one 8 GB ram. The purpose for doing so is to save some money now and still have the option to update to 16 GB later if necessary.

    If you have tried this configuration, could you please share which ram you bought and how your MBP runs? Thank you.
     
  2. JTToft macrumors 68040

    Joined:
    Apr 27, 2010
    Location:
    Aarhus, Denmark
    #2
    - I plan on doing the same on my early 2011 MacBook Pro in the near future. It should work just fine.
    I will most likely buy Corsair Vengeance RAM.
     
  3. Mr MM macrumors 65816

    Mr MM

    Joined:
    Jun 29, 2011
    #3
    any 1600mhz ram should work. I like crucial a lot.
     
  4. ugp macrumors 65816

    ugp

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    Jan 7, 2008
    Location:
    Inverness, Florida
    #4
    For best performance you better to run two identical chips in pairs.
     
  5. liya1201 thread starter macrumors member

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    Sep 8, 2010
  6. sweetbrat macrumors 65816

    sweetbrat

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    Jun 17, 2009
    Location:
    Redford, MI
    #6
    Running two chips that are the same does give slightly better performance, but if I remember right it's not that huge of a difference. The decrease in performance you'd see if you're regularly running out of RAM and having a lot of page-outs is likely to be much more noticeable. So even with unmatched RAM, you'd still be better off than not upgrading the RAM at all. If you eventually plan on going to 16GB, I'd go ahead and get the one 8GB chip now.
     
  7. Mr MM macrumors 65816

    Mr MM

    Joined:
    Jun 29, 2011
    #7
    you mean running pure dual channel?
    if it is, there is for a long time hybrid dual channels, i,e, RAM of different sizes, paired.

    Another problem is that dual channel memory type was developed because sometime ago the RAM was the bottleneck of the cpu, now it isnt.

    I will guarantee that the OP will feel the difference of a SSD (which right now is the bottleneck) to the difference in performance that the hybrid dual channel should offer.

    here is a table of access times, counted in cpu cycles, its a dated table though


    LEVEL ACCESS TIME TYPICAL SIZE
    Registers "instantaneous" under 1KB
    Level 1 Cache 1-3 ns 64KB per core
    Level 2 Cache 3-10 ns 256KB per core
    Level 3 Cache 10-20 ns 2-20 MB per chip
    Main Memory 30-60 ns 4-32 GB per system
    Hard Disk 3,000,000-10,000,000 ns over 1TB

    it was taken from here:
    http://arstechnica.com/information-...revolution-how-solid-state-disks-really-work/

    so yeah dual channel, tri channel or quad channel only matter in very specific loads, imagine 256gb of RAM needed specific load, still due to type of load the speed wont matter that much, but the amount will.
     
  8. yusukeaoki macrumors 68030

    yusukeaoki

    Joined:
    Mar 22, 2011
    Location:
    Tokyo, Japan
    #8
    For the best results, you must have the 2 same RAM.
    But it wouldnt be as noticeable depending on your usage.
     
  9. Southernboyj macrumors 68000

    Southernboyj

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    Mar 8, 2012
    Location:
    Mobile, AL
    #9
    As others have said, since it's the same channel performance would be better if you used the same chip on both.
     
  10. biohead macrumors 6502

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    Jun 18, 2010
    Location:
    West Drayton, UK
    #10
    Yes it's fine. Currently doing that myself as I ordered two sticks of corsair vengeance 1600MHz - one was faulty so whilst I wait for a replacement I shoved one of the standard 2gb sticks in.

    Only thing is it currently shows it running as 1333Mhz rather than 1600mhz.
     
  11. Orihara macrumors newbie

    Joined:
    Jul 7, 2012
    Location:
    Adelaide, Australia
    #11
    There's nothing wrong with it however it's sub optimal.
    Using 2 identical sticks allows memory to be written in an interpolated manner
    ie: 1 bit on one stick, one bit on the other stick, etc
    since the sticks are the same size this then works out perfectly and allows you to read files back at twice the speed from ram because you're reading from 2 sources.

    the way you set it up you'll have 4gig interpolated and 6 gig not. meaning after 4 gig of ram usage (assuming OS X/Windows handles it properly) the speed with which you can read back from memory will drop significantly (theoretically 50%, realistically probably less)

    that being said, the hit in performance isn't "huge" and still much, much faster than reading back from hard disks obviously. RAM is more than fast enough at read operations for this to affect general usage much.
     
  12. liya1201 thread starter macrumors member

    Joined:
    Sep 8, 2010
    #12
    That's interesting and I wonder what caused the down speed from 1600 mhz to 1333 mhz though. By the way, do you experience any lagging, beach balling, freezing, and/or crashing in this 8 GB + 2 GB configuration. Thanks!

    I also like to thank all others who provided detailed explanation regarding the performance of dual channel memory.
     
  13. biohead macrumors 6502

    Joined:
    Jun 18, 2010
    Location:
    West Drayton, UK
    #13
    No lagging, no beach balling or anything of the sorts. Both sticks are 1600MHz, so it is indeed a bit strange for it to down clock to 1333MHz when the sticks aren't matched.
     

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