Maximum RAM for Boot Camp on MacPro

Discussion in 'Windows, Linux & Others on the Mac' started by NedMacPro, Aug 22, 2006.

  1. NedMacPro macrumors newbie

    Aug 22, 2006
    I have 5 GB RAM that shows up just fine on the OS X but in Boot Camp it is only showing 1.98...anybody know why?
  2. Anonymous Freak macrumors 601

    Anonymous Freak

    Dec 12, 2002
    Windows is 32-bit.

    Because Windows XP Home and Professional editions are only 32-bit, they have an inherent limitation of 4 GB. However, by default, they only show up to 2 GB as 'user-addressable'. This can be increased to 3 GB by adding the '/3GB' switch to your boot.ini listing. Usually, XP reserves anything over 2 GB for system use. (And, yes, 3 GB is the absolute max that XP Pro will allow to be seen by applications.)

    See here, 4th through 7th paragraphs.

    Another possible workaround is to install the 64-bit version of Windows, Windows XP Professional x64 Edition. (Although I don't know if Boot Camp supports it...)
  3. dextertangocci macrumors 68000

    Apr 2, 2006
    The problem:

    windoze;) :rolleyes:

    Is it the 32 bit version of xp? If so, I think it will only recognise 4GB RAM.

    I hve no idea why it doesn't evn recognise 2:confused:
  4. NedMacPro thread starter macrumors newbie

    Aug 22, 2006
    Thx for the info...

    Thx for the info...I will try this...
  5. Trip.Tucker Guest

    Mar 13, 2008
    Accepted answer:

  6. CanadaRAM macrumors G5


    Oct 11, 2004
    On the Left Coast - Victoria BC Canada
    the /3GB switch in Windows on a PC affects only the amount of RAM that is allocatable to applications (and only if the application is coded to take advantage of it, few are), not the total RAM visible / usable by the OS.

    The Bootcamp / EFI firmware of the Mac Pro limits the RAM Usable in 32-bit Windows to 2 GB. The /3GB and PAE switches have nothing to do with the amount of RAM accessible by Windows under Bootcamp.
  7. mosx macrumors 65816

    Mar 3, 2007

    Also, the 32-bit version of Windows (XP and Vista) can address 3GB. Not 2GB.

    Seeing less than 3GB when 3GB or more is installed is always the fault of the chipset, not the OS.

    64-bit Windows can address 4GB and above. Vista Home Premium has something like a 16GB limit.
  8. nurfen macrumors member

    Jan 21, 2007
    What? So, if I run Vista x64, I still can't use my 6 GBs of RAM?
  9. 617arg macrumors 6502

    Mar 3, 2008
    You can. When I run Vista x64 through Bootcamp I can see all 18GB of my RAM. When I'm running through Fusion I have 8GB allocated, and it shows up.
  10. Siron macrumors 6502


    Feb 4, 2008
    North Carolina
    I have Vista Business (to use 8 cores) 64 bit (to see all RAM - I have 4GB and it sees all of it). My XP Pro 32 only saw 3GB. Go with Vista Business 64. Forget about the 'Vista sucks' posts - I have had no problems whatsoever and it runs faster than XP 32.
  11. steveza macrumors 68000


    Feb 20, 2008
    Agreed - get Vista x64 (any version other than Home Basic/Premuim) and your RAM and processors will be available to you.

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