Memory Question

Discussion in 'Windows 64bit' started by Martin Racette, May 12, 2006.

  1. Hi,

    I nstalled 4Gb of RAM, using XP Pro 32bit, and Windows is only detecting 2.5Gb,
    I was told that if I installed and use XP Pro x64, I would be able to use the
    whole 4Gb, is this correct ?

    --
    Thank you in Advance

    Merci a l'Avance

    Martin
    Martin Racette, May 12, 2006
    #1
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  2. Martin Racette

    DieterS Guest

    Hi Martin

    I am surprised, that you got only 2.5GB out of your 32bit System. Here it
    was 3.1GB, approx. the same amount as with the x64 edition. But I agree, the
    memory usage is strange and some folks advised here also, that with x64 I
    could use the full 4GB of RAM!

    Regards
    Dieter

    "Martin Racette" <> wrote in message
    news:...
    > Hi,
    >
    > I nstalled 4Gb of RAM, using XP Pro 32bit, and Windows is only detecting
    > 2.5Gb, I was told that if I installed and use XP Pro x64, I would be able
    > to use the whole 4Gb, is this correct ?
    >
    > --
    > Thank you in Advance
    >
    > Merci a l'Avance
    >
    > Martin
    >
    >
    DieterS, May 12, 2006
    #2
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  3. Part of the answer to that will depend on the motherboard. You'll lose some
    regardless, since the mobo must support remapping the address space for the
    PCI card BIOSs

    --
    Charlie.
    http://msmvps.com/xperts64

    Martin Racette wrote:
    > Hi,
    >
    > I nstalled 4Gb of RAM, using XP Pro 32bit, and Windows is only detecting
    > 2.5Gb, I was told that if I installed and use XP Pro x64, I would be able
    > to use the whole 4Gb, is this correct ?
    Charlie Russel - MVP, May 13, 2006
    #3
  4. Hi,

    Can explain to me, in lanment terms, why is that that we loose memory when we
    use PCI device, I can not see the relation between the two of them beside the
    fact that they are both connect to the motherboard.



    --
    Thank you in Advance

    Merci a l'Avance

    Martin

    "Charlie Russel - MVP" <> wrote in message
    news:...
    > Part of the answer to that will depend on the motherboard. You'll lose some
    > regardless, since the mobo must support remapping the address space for the
    > PCI card BIOSs
    >
    > --
    > Charlie.
    > http://msmvps.com/xperts64
    >
    > Martin Racette wrote:
    >> Hi,
    >>
    >> I nstalled 4Gb of RAM, using XP Pro 32bit, and Windows is only detecting
    >> 2.5Gb, I was told that if I installed and use XP Pro x64, I would be able
    >> to use the whole 4Gb, is this correct ?

    >
    >
    Martin Racette, May 13, 2006
    #4
  5. PCI cards often have BIOSs that control their behaviour. Those BIOSs must
    have a memory address (they are a form of memory, just as RAM is) that the
    device can use. Since they must work in 32-bit Windows as well as 64-bit
    Windows, and 32-bit Windows is limited to 4 GB of directly addressable
    memory, they must have an address in that first 4 GB of memory. The area
    above 2 GB is used by them, since 32-bit Windows reserves the address space
    above 2GB for the operating system to use. (I go into a good deal more
    detail about this in several of my whitepapers and columns. See the links
    off my blog site.)

    --
    Charlie.
    http://msmvps.com/xperts64

    Martin Racette wrote:
    > Hi,
    >
    > Can explain to me, in lanment terms, why is that that we loose memory
    > when we use PCI device, I can not see the relation between the two of
    > them beside the fact that they are both connect to the motherboard.
    >
    >
    >
    >
    > "Charlie Russel - MVP" <> wrote in message
    > news:...
    >> Part of the answer to that will depend on the motherboard. You'll lose
    >> some regardless, since the mobo must support remapping the address space
    >> for the PCI card BIOSs
    >>
    >> --
    >> Charlie.
    >> http://msmvps.com/xperts64
    >>
    >> Martin Racette wrote:
    >>> Hi,
    >>>
    >>> I nstalled 4Gb of RAM, using XP Pro 32bit, and Windows is only detecting
    >>> 2.5Gb, I was told that if I installed and use XP Pro x64, I would be
    >>> able to use the whole 4Gb, is this correct ?
    Charlie Russel - MVP, May 13, 2006
    #5
  6. Martin Racette wrote:
    > Can explain to me, in lanment terms, why is that that we loose memory

    when we
    > use PCI device, I can not see the relation between the two of them

    beside the
    > fact that they are both connect to the motherboard.


    The connection is that PCI can also have memory, such as your graphics
    card. It needs to be addressed by the CPU, so it is cutting into the 4GB
    of memory that a CPU can address in 32bit mode (without tricks). The
    amount of memory space reserved for PCI devices differs, it is usually
    something like 512 MB or 1GB.

    With a 64bit OS installed, there is no relevant address limit, so you
    should be able to use all 4GB (or more). However, as Charlie pointed
    out, there are stupid motherboard designs where the memory space using
    by PCI bus "hides" the same amount of real memory. In that case you
    would only see a significant improvement if you install more memory.

    Thomas
    Thomas Steffen, May 14, 2006
    #6
  7. Thank to all for the information, it is a lot clearer now than when I installed
    the memory and lost half of it

    --
    Thank you in Advance

    Merci a l'Avance

    Martin

    "Thomas Steffen" <> wrote in message
    news:...
    > Martin Racette wrote:
    > > Can explain to me, in lanment terms, why is that that we loose memory

    > when we
    > > use PCI device, I can not see the relation between the two of them

    > beside the
    > > fact that they are both connect to the motherboard.

    >
    > The connection is that PCI can also have memory, such as your graphics card.
    > It needs to be addressed by the CPU, so it is cutting into the 4GB of memory
    > that a CPU can address in 32bit mode (without tricks). The amount of memory
    > space reserved for PCI devices differs, it is usually something like 512 MB or
    > 1GB.
    >
    > With a 64bit OS installed, there is no relevant address limit, so you should
    > be able to use all 4GB (or more). However, as Charlie pointed out, there are
    > stupid motherboard designs where the memory space using by PCI bus "hides" the
    > same amount of real memory. In that case you would only see a significant
    > improvement if you install more memory.
    >
    > Thomas
    Martin Racette, May 15, 2006
    #7
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