64 bit Windows on '06 C2D 4GB RAM?

Discussion in 'Mac Basics and Help' started by 2ms, Jun 7, 2009.

  1. 2ms macrumors 6502

    Joined:
    Nov 22, 2002
    #1
    I have a late 06 20" iMac with 2.16 GHz C2D. I have 4 GB of ram in it, but I seem to recall that the Intel chipset or something was not able to make more than 3 GB or something actually available to the system.

    Is this true?

    If so, that sucks, because I hear that the main speed improvements in using 64-bit Windows over 32-bit come when you have 4GB ram. I just installed Windows 7 RC 64-bit in hopes of it making my CAD work go a little smoother/faster, which is what other CAD people say it indeed does, at least if you have 4GB ram.
     
  2. madog macrumors 65816

    madog

    Joined:
    Nov 25, 2004
    Location:
    Korova Milkbar
    #2
    From Microsoft:

    Also:
    The problem is, that with 4GB of RAM loaded up in XP, the system will only recognize ~3.25GB, so people don't think it can utilize a full 4GB. However,
    So the OS itself has 2GB, and other applications share that 2GB, but then also get their own "virtual" 2GB as well. The 4GT option noted at the top of the page changes that from 2GB to 3GB "blocks".

    Also, I don't believe 64bit XP is supported natively with Bootcamp drivers, but Vista 64bit is.

    P.S. PAE was enabled on my MBP by default.

    Edit: It's also due to MS changing PAE in XP SP2, and could be referred to as a "bug". I couldn't find the link before, but it's at the top of the references.

    MS: Incorrect RAM reported

    the-4gb-windows-memory-limit-what-does-it-really-mean.aspx

    MS: Windows Memory Limits

    MS: PAE
     
  3. 2ms thread starter macrumors 6502

    Joined:
    Nov 22, 2002
    #3
    Is there a RAM utilization limit in my hardware though? I have confirmed that Windows 7 64-bit (what I'm using) will utilize 4 GB of RAM.

    However, I seem to recall that my 2.16GHz iMac (that generation of Intel chipsets) is NOT able to utilize more than 3 GB ram. It's just a vague recollection though.

    Is there in fact this hardware limitation, or was there only ever a Windows software limitation?
     
  4. TBi macrumors 68030

    TBi

    Joined:
    Jul 26, 2005
    Location:
    Ireland
    #4
    It can be both. It depends on your hardware. The easiest way to find out is to check Intel's website for the chipset you have. They have all the datasheet's detailing the max ram you can put on it.

    There could be a hardware limit imposed by Apple if they don't use all the memory address lines. Basically if you can see 4GB in OSX then you can see it all in 64 bit windows.
     
  5. madog macrumors 65816

    madog

    Joined:
    Nov 25, 2004
    Location:
    Korova Milkbar
    #5
    The PAE feature is limited by hardware, but I believe the C2D Intels that Apples uses can utilize it.
     

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