Why no more than 4GB of ram in the laptops now that they're 64 bit?

Discussion in 'MacBook Pro' started by marklight, Jan 25, 2008.

  1. marklight macrumors 6502

    Apr 6, 2006
    The mac pros can handle 32 GB. Why can't I stick in 2 4GB sticks into my macbook/macbook pro?

    What is the limiting factor?
  2. Eidorian macrumors Penryn


    Mar 23, 2005
    I'd like to know where I could get some DDR2-667 4GB SODIMMs. :D
  3. heatmiser macrumors 68020

    Dec 6, 2007
  4. Stridder44 macrumors 68040


    Mar 24, 2003
    Because most notebooks only have 2 RAM slots.

    4GB RAM sticks are insanely expensive right now, if they're even available at all (for notebooks).
  5. marklight thread starter macrumors 6502

    Apr 6, 2006

    why is the chipset the limiting factor? It's 64 bit right?
  6. sknighti macrumors newbie

    Jan 19, 2008
    the software is 64-bit
    the hardware is unaffected whether it is 32-bit or 64-bit OS, its the physical limitation of the chipset itself
  7. Brianstorm91 macrumors 65816


    Sep 30, 2007
    Cambridge, UK
    I take it you've found some 4GB sticks of RAM then?
  8. lshirase macrumors regular

    Jan 7, 2008
  9. gnasher729 macrumors P6


    Nov 25, 2005
    Two factors: The chipset in the MacBook cannot handle more than 4 GB (not sure if the limit is 4 GB, but the limit is definitely 2 chips, and you can't find any fitting chips larger than 2GB), and space - there is only space for two relatively small SODIMM chips. The Mac Pro has space for eight chips.
  10. John.B macrumors 601


    Jan 15, 2008
    Holocene Epoch
    The difference is between the limits of how much memory is theoretically addressable in a 64-bit address space vs. the physical limitations of the actual chipset. In this case Apple is using the Santa Rosa chipset which has an inherent 8 GB physical limit for the iMac/Macbook/Macbook Pro lines. As other's have said, until someone ramps up production on 4 GB 200 pin SO-DIMMs that will fit into the tiny space available, you'll have to settle for two 2 GB SO-DIMMs (for a max. of 4 GB).

    "Most 64-bit consumer PCs on the market today have an artificial limit on the amount of memory they can recognize, because physical constraints make it highly unlikely that one will need support for the full 16.8 million terabyte capacity. Apple's Mac Pro, for example, can be physically configured with up to 32 gigabytes of memory, and as such there is no need for support beyond that amount.[1]"
  11. iPhil macrumors 68040



    There's the answer to 8GB of Ram Q.
  12. 147798 Suspended

    Dec 29, 2007
    Just curious -- is anyone exceeding 4GB regularly on their MacBook? (I could maybe see MacBook Pro. Still, OSX ain't MS Vista). I haven't even gone past 3GB yet with multiple apps open and video processing.
  13. pseudonymph macrumors member

    Aug 10, 2007
    I have 4gb installed and most of the time I have a good 1-2gb free, even with a ton of apps open while I'm working. I used to hit limits every so often on my last laptop that had 2gb installed but I haven't come close with 4.

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