Can I give my Rev A MacBook Pro 3gb of RAM?

Discussion in 'MacBook Pro' started by Killyp, Oct 24, 2006.

  1. Killyp macrumors 68040


    Jun 14, 2006
    The new MacBook Pros can take 3 gb of RAM according to Apple, but can the Rev A ones? I'd like to give my 1.83 some more to play with, as it lags when I'm using very large (audio) files...
  2. dmw007 macrumors G4


    May 26, 2005
    Working for MI-6

    As far as I know, the chipset on the logic board limits you to 2GBs of RAM. :eek:
  3. SoLibertyDies macrumors regular

    Oct 16, 2006
    Spanaway, Wa
  4. Killyp thread starter macrumors 68040


    Jun 14, 2006
  5. garfield2002 macrumors regular

    Oct 31, 2003
    I wonder if some brave soul who is getting a C2D machine with 3GB to replace their Rev A MBP would be willing try their 2GB stick in it to make sure. ;)

    Incidently, the announcement made me look at 2GB RAM prices, I am just amazed at how expensive they are. :eek:

    I'm also curious of the 3GB limit, why not 4GB? I would think two RAM slots at 2x2GB makes more sense, well, if you had the cash. Perhaps one slot cannot physically accept a 2gig stick?
  6. ksz macrumors 68000

    Oct 28, 2003
    San Jose, CA
    I think 1GB is soldered on the motherboard, leaving only 1 memory slot that can accommodate either 1GB DIMM or 2GB DIMM.

    EDIT: Tech Specs state there are 2 SO-DIMM slots, but only 3GB possible.
  7. skunk macrumors G4


    Jun 29, 2002
    Republic of Ukistan
    It's the same as with the iMac: you can put 4GB in, but it'll only use 3. A limitation of the C2D, I believe.
  8. jeff127 macrumors member

    Apr 10, 2006

    From the above thread:
    1x 2GB stick works fine on its own,
    1x 2GB + 1x 1GB doesn't work
    2x 2GB (!!!) doesn't work either.

  9. garfield2002 macrumors regular

    Oct 31, 2003
    Thanks for the link jeff. :) That makes more sense. Boo. :)
  10. Shadow macrumors 68000


    Feb 17, 2006
    Keele, United Kingdom
    So much for 64 bit...:rolleyes:
  11. Bill Gates macrumors 68020

    Bill Gates

    Jun 21, 2006
    There's more to 64-bit than the ability to address large amounts of memory. It's a limitation of the Napa platform.
  12. robbieduncan Moderator emeritus


    Jul 24, 2002
    Exactly. Intel CPUs do not have an on-die memory controller (unlike recent AMD ones). So the CPU communicates with the north-bridge which has the memory controller.

    In the case of the MBP and the iMac the memory controller is 32-bit. So the maximum total memory space is 4Gb. As some if this has to be reserved for memory mapping peripherals, DMA transfer addresses and the like there is only 3Gb available for addressing user memory.

    The chipset used for the Mac Pro allows for greater than 32-bit addressing (but it's still not full 64-bit) allowing for more than 4Gb of user RAM (16Gb in the Mac Pro, but interestingly 32Gb in the new Intel XServe, so perhaps the Mac Pro can actually cope with 32Gb).
  13. NJuul macrumors 6502

    Mar 15, 2006
    Lucky bastard...;)
  14. barefeats macrumors 65816


    Jul 6, 2000
    Interleaving issue

    I'm not so concerned about being limited to 3GB on the new MacBook Pro Core 2 Duo. What concerns me is the loss of interleaving when you install unmatched memory pairs.

    If cost is no object, it would seem that installing two 2GB modules would be desirable even if you only see 3GB. That restores the interleaving.
  15. Transeau macrumors 6502a


    Jan 18, 2005
    Alta Loma, CA
    The 3GB limit is a limit of the current chipset.
    The addressing of the current chipset puts the video and disk controllers in the 3~4GB memory space, so the overlap prevents the use of this range.

    The limit will be removed with the "Santa Rosa" chipset next year sometime. Though a new chipset means a new motherboard design, which means a whole new development and test cycle.

    If 4+GB is important to you in a notebook, it may be better for you to wait until the next rev of MBP comes... (I'm guessing 2Q07)

    As for dual channel mode with 3GB, yes it will revert back single channel dropping you back to a 64-Bit memory bus. You will have to weigh the differences... 128-Bit memory (2x the memory speed) or 1 more GB of memory?

    Do you need the memory? Check you Page Outs in the Activity Monitor.
    if you see a zero, you have more than enough already. Low numbers (anything below 5000?) is still fine. Do a clean boot, run the apps that you would normally use, then check the Page Outs.. if it's still low, then there is no need to spend the money.

    Attached Files:

  16. nicksoper macrumors member


    Mar 6, 2006
    Cape Town
    Dual Channel Memory

    I was keen to try and get 3Gb in my 17inch macbook pro, so it looks like I will have to upgrade to only 2gb :p

    I was wondering though, is there any way to check if your memory is running with both channels? And is there any whay to know which supplier's ram will work at dual channle with the RAM already in my mac book.

    What is the perfomace loss from dual channel to just one?

  17. Sun Baked macrumors G5

    Sun Baked

    May 19, 2002
    Something like drop from 10600 MB/sec to 5300 MB/sec.

    But this is still a lot less noticeable than the drop from 5300 MB/sec to 50 MB/sec when you don't have enough memory.

    While 10600 MB/sec is fast, but you won't notice it as much as if you would if the virtual memory manager kicks in and you chugs along at the pokey 50 MB/sec that the HD operates at.

    Basically, more memory will trump dual channel matched memory if you really are a power user. Dual channel is a fraction of a second quicker, and not enough memory is a beachball that lasts for seconds.
  18. nicksoper macrumors member


    Mar 6, 2006
    Cape Town
    Dual Channel Ram

    Cheers Sunbaked. :cool:

    That was a really a really good thing to know, well explained (apart from the beach ball analogy)

    Has anyone else got a clue if you can check if your new stick of ram will work at dual channel speed in your mac? OR once its in, if it is running at dual channel!

    Nice to know that it will still be fast though.

  19. Jkirk3279 macrumors newbie

    Feb 28, 2010

    So from what I've read, the Intel 945PM chip CAN address more than 2GB, but the firmware on the logic board of a Spring 2006 MBPro was written for 2GB and no more.

    It would be a nice present from Mr. Jobs if we got a Firmware Update to fix this...

    I'm in college and can't really afford to replace this 4 yr old Mac at the moment.

    Yet running Parallels is kind of important, and it crawls unless I shut down everything else.

  20. Bill Gates macrumors 68020

    Bill Gates

    Jun 21, 2006
    It's not going to happen. Ollllllddddd thread by the way.

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