Re: OS for 4GB RAM

Discussion in 'Computer Information' started by sandy58, Apr 2, 2010.

  1. sandy58

    sandy58 Guest

    On Apr 2, 7:55 pm, "James D. Andrews" <> wrote:
    > Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work?  I was
    > reading today that the 32-bit will only support 3GB.  Don't know how true
    > that is.
    >
    > I suppose it would be nice to know before I go and buy an OS.
    >
    > --- news://freenews.netfront.net/ - complaints: ---


    32-bit won't use 4gb ram. 3gb is about it.
    64-bit will use as much as you can get in.
    sandy58, Apr 2, 2010
    #1
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  2. "sandy58" <> wrote in message
    news:...
    On Apr 2, 7:55 pm, "James D. Andrews" <> wrote:
    > Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was
    > reading today that the 32-bit will only support 3GB. Don't know how true
    > that is.
    >
    > I suppose it would be nice to know before I go and buy an OS.
    >
    > --- news://freenews.netfront.net/ - complaints: ---


    32-bit won't use 4gb ram. 3gb is about it.
    64-bit will use as much as you can get in.

    <JS>
    I'm using all 4G of RAM in my machine. I have 32-bit XP Pro.



    </JS>
    Jeff Strickland, Apr 3, 2010
    #2
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  3. sandy58

    gnu / linux Guest

    On Apr 2, 7:12 pm, "Jeff Strickland" <> wrote:
    > "sandy58" <> wrote in message
    >
    > news:...
    > On Apr 2, 7:55 pm, "James D. Andrews" <> wrote:
    >
    > > Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was
    > > reading today that the 32-bit will only support 3GB. Don't know how true
    > > that is.

    >
    > > I suppose it would be nice to know before I go and buy an OS.

    >
    > > --- news://freenews.netfront.net/ - complaints: ---

    >
    > 32-bit won't use 4gb ram. 3gb is about it.
    > 64-bit will use as much as you can get in.
    >
    > <JS>
    > I'm using all 4G of RAM in my machine. I have 32-bit XP Pro.
    >
    > </JS>


    32 bit will use most all of the 4 GB
    gnu / linux, Apr 3, 2010
    #3
  4. "gnu / linux" <> wrote in message
    news:...
    On Apr 2, 7:12 pm, "Jeff Strickland" <> wrote:
    > "sandy58" <> wrote in message
    >
    > news:...
    > On Apr 2, 7:55 pm, "James D. Andrews" <> wrote:
    >
    > > Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was
    > > reading today that the 32-bit will only support 3GB. Don't know how true
    > > that is.

    >
    > > I suppose it would be nice to know before I go and buy an OS.

    >
    > > --- news://freenews.netfront.net/ - complaints: ---

    >
    > 32-bit won't use 4gb ram. 3gb is about it.
    > 64-bit will use as much as you can get in.
    >
    > <JS>
    > I'm using all 4G of RAM in my machine. I have 32-bit XP Pro.
    >
    > </JS>


    32 bit will use most all of the 4 GB



    <JS>
    That's my point. The person I was replying to said that only 3G is supported
    by 32-bit systems.

    </JS>
    Jeff Strickland, Apr 3, 2010
    #4
  5. sandy58

    Paul Guest

    Jeff Strickland wrote:
    > "gnu / linux" <> wrote in message
    > news:...
    > On Apr 2, 7:12 pm, "Jeff Strickland" <> wrote:
    >> "sandy58" <> wrote in message
    >>
    >> news:...
    >> On Apr 2, 7:55 pm, "James D. Andrews" <> wrote:
    >>
    >>> Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was
    >>> reading today that the 32-bit will only support 3GB. Don't know how true
    >>> that is.
    >>> I suppose it would be nice to know before I go and buy an OS.

    >> 32-bit won't use 4gb ram. 3gb is about it.
    >> 64-bit will use as much as you can get in.
    >>
    >> <JS>
    >> I'm using all 4G of RAM in my machine. I have 32-bit XP Pro.
    >>
    >> </JS>

    >
    > 32 bit will use most all of the 4 GB
    >
    >
    >
    > <JS>
    > That's my point. The person I was replying to said that only 3G is supported
    > by 32-bit systems.
    >
    > </JS>
    >


    This depends a lot, on the details.

    As JS mentioned via a link at the end of his posting, there is a
    hardware feature called PAE, that maps 32 bit addresses to a 36 bit
    physical address space. Intel processors and chipsets have had PAE
    capability for some time. And PAE allows a 32 bit OS to address up to
    64GB of installed memory. (Modern PAE can support more than 36 bits,
    so more is possible. For example, on modern AMD processors, it goes
    to 40 bits.)

    It is possible that some early version of WinXP, still properly supported
    PAE. But in later Service Packs, a bit was borrowed for something like NX
    (no execute) bit. That was a security feature. At the same time, they
    decided it would be fun to prevent PAE from accessing more than 4GB.
    I'm a little fuzzy on the details.

    There is a discussion about this topic, here. This person hacked an MS
    OS, to prove that more than 4GB can be addressed by a 32 bit OS. It works.

    http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm

    So, if the OS has PAE neutered, then indeed there might be only
    4GB of address space available via the 32 bit OS. From that, the
    hardware devices (like the memory on the video card), has to be
    addressable. And after all the addresses for the various hardware
    busses have been assigned by the BIOS, the remainder is used to
    provide access to the memory DIMMs. If you install 4GB worth of DIMMs,
    and happened to use an old PCI video card with small resident memory,
    you might see reported that you have 3.5GB free. (Bus address space
    is assigned in 256MB chunks, and with PCI/AGP or PCI/PCI Express,
    you might lose two chunks to start with. Once the actual hardware
    rolls over that assignment, another chunk would be mapped in. So
    the assignment process has a relatively coarse granularity.)

    If you install a couple Nvidia video cards in SLI, with 512MB of
    memory on each card, and happen to have 4GB memory installed,
    and have the neutered OS running, then the free memory reported
    once the OS is running, could be as low as 2.75GB (someone reported
    that, on an S939 board). Which negates the purpose of installing
    that much memory to begin with. If you had a monster video setup,
    you might be better off installing 2x1GB + 2x512MB sticks, for a
    total of 3GB dual channel mode. And then, you'd still see the
    2.75GB free reported, and would only be losing 0.25GB.

    Or, you could use a 64 bit OS, and have it all.

    In terms of the memory configuration, a lot of people would choose
    to use 2x2GB, as it may support a higher max operating frequency
    for the DIMMs. And then take the loss, on whatever amount of memory
    is inaccessible by the OS. Using a four stick configuration, might
    not clock quite as high.

    The details are a bit fuzzy, as to whether there is a good reason
    for PAE to not work on WinXP x32. But it would certainly push
    sales of alternate OS solutions. (And no, WinXP x64 is not a good
    choice. It was a little rough around the edges.)

    If you use PAE, one of the limitations would be, that a single
    program could not use all the memory on the computer. If you
    had 8GB of RAM installed, used a 32 bit OS, you would need
    two programs, accessing 4GB each, to use all the memory.
    There might even be further restrictions, as to the maximum
    memory that any program or process could use (user/kernel split?).
    So even if PAE was working, it is a less ideal situation than using a
    64 bit OS to solve the addressing limitations. But PAE
    does have the advantage, that it has been available in hardware
    for a long time. It is only now, that ordinary desktops
    can easily reach those memory limits.

    http://en.wikipedia.org/wiki/Physical_Address_Extension

    "Windows XP Service Pack 2 and later, by default, on processors
    with the no-execute (NX) or execute-disable (XD) feature, runs
    in PAE mode in order to allow NX. The no execute (NX, or XD for
    execution disable) bit resides in bit 63 of the page table entry
    and, without PAE, page table entries on 32-bit systems have only
    32 bits; therefore PAE mode is required if the NX feature is to
    be exploited.

    However, "client" versions of 32-bit Windows (Windows XP, Windows
    Vista, Windows 7) limit physical address space to the first 4 GB
    for driver compatibility and *licensing* reasons, even though these
    versions do run in PAE mode if NX support is enabled."

    So that tells you, the limitation is artificial.

    There are some other things to consider, before making the OS choice.
    For example, how much memory does the software you own, want to use ?
    I have a copy of Photoshop, that won't go above 1.8GB on a 4GB system.
    For the people that own large quantities of memory, I'd be interested
    in what exactly they've been able to get out of it. I wasted a couple
    hours on the topic and gave up (my machine is back to 2GB now). I
    don't seem to have anything which is IMAGE_FILE_LARGE_ADDRESS_AWARE.
    I could certainly run a couple different programs, to use the RAM,
    such as some VPC2007 sessions. And that is the most likely thing
    here, that would benefit from 4GB. For a lot of other stuff, 2GB
    is enough for me.

    http://en.wikipedia.org/wiki/RAM_Limit

    A 64 bit OS, makes some of the issues more transparent. But does
    not guarantee that a single program can use all available memory.
    For example, if you have a 64 bit executable, running on a 64 bit
    OS, that removes the limits. But other combinations could
    still have limits, like running existing 32 bit programs on
    a 64 bit OS.

    "Memory Limits for Windows Releases"
    http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx

    Paul
    Paul, Apr 3, 2010
    #5
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