x64 vs Win 2003 Enteprrise, <= 32GB RAM

Discussion in 'Windows 64bit' started by bill, Mar 1, 2006.

  1. bill

    bill Guest

    What are the advantages of an x64 OS vs. a Windows 2003 Enterprise server if
    one has 32GB or less RAM?
    (The Enterprise can address 32GB of RAM)

    I think the biggie is not just the amount of RAM but the x64 box can address
    the memory as a single 64-bit offset (from a base register) and doesn't need
    32-bit workarounds like AWE.

    I also read that x64 CPU hardware stops certain types of "buffer overrun"
    attacks that are possible with 32-bit CPU?

    Can you add any other items to this list.(or maybe correct my above
    statements if they are wrong.)


    TIA,

    Bill
    bill, Mar 1, 2006
    #1
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  2. Well, as you point out, the RAM is directly addressable. But more than that,
    it can run 64-bit versions of software which can also directly address that
    RAM, and have access to 8TB of virtual memory address space. Finally, even
    32-bit programs that are written to address memory >2GB will have access to
    a full 4GB of directly addressable virtual memory address space, instead of
    a maximum of 3GB (directly addressable) on 32-bit Windows.

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

    bill wrote:
    > What are the advantages of an x64 OS vs. a Windows 2003 Enterprise server
    > if one has 32GB or less RAM?
    > (The Enterprise can address 32GB of RAM)
    >
    > I think the biggie is not just the amount of RAM but the x64 box can
    > address the memory as a single 64-bit offset (from a base register) and
    > doesn't need 32-bit workarounds like AWE.
    >
    > I also read that x64 CPU hardware stops certain types of "buffer overrun"
    > attacks that are possible with 32-bit CPU?
    >
    > Can you add any other items to this list.(or maybe correct my above
    > statements if they are wrong.)
    >
    >
    > TIA,
    >
    > Bill
    Charlie Russel - MVP, Mar 1, 2006
    #2
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  3. Hi Charlie

    I am just wondering if it's the 8TB or 16TB of virtual memory address space
    that a 64bit processor can address on a 64bit Operating System (Microsoft
    x64)? Is there any other Operating System in the market that can address more
    than 16TB of virtual address memory that Microsoft Windows x64 does? This is
    because 2^64 is 1.8447 x 10^19.

    Thanks
    Hemanth


    "Charlie Russel - MVP" wrote:

    > Well, as you point out, the RAM is directly addressable. But more than that,
    > it can run 64-bit versions of software which can also directly address that
    > RAM, and have access to 8TB of virtual memory address space. Finally, even
    > 32-bit programs that are written to address memory >2GB will have access to
    > a full 4GB of directly addressable virtual memory address space, instead of
    > a maximum of 3GB (directly addressable) on 32-bit Windows.
    >
    > --
    > Charlie.
    > http://msmvps.com/xperts64
    >
    > bill wrote:
    > > What are the advantages of an x64 OS vs. a Windows 2003 Enterprise server
    > > if one has 32GB or less RAM?
    > > (The Enterprise can address 32GB of RAM)
    > >
    > > I think the biggie is not just the amount of RAM but the x64 box can
    > > address the memory as a single 64-bit offset (from a base register) and
    > > doesn't need 32-bit workarounds like AWE.
    > >
    > > I also read that x64 CPU hardware stops certain types of "buffer overrun"
    > > attacks that are possible with 32-bit CPU?
    > >
    > > Can you add any other items to this list.(or maybe correct my above
    > > statements if they are wrong.)
    > >
    > >
    > > TIA,
    > >
    > > Bill

    >
    >
    >
    =?Utf-8?B?SGVtYW50aA==?=, Mar 2, 2006
    #3
  4. I believe Itanium can address more, but I don't really play in that space,
    so don't know. The number of address lines on the amd64 architecture (ie,
    x64) is not the full 64-bits worth. Thus the limitation of 16 TB. By the
    time that gets to be a limitation, I suspect the architecture of the x64
    will have shifted a bit, and it will address more.

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

    Hemanth wrote:
    > Hi Charlie
    >
    > I am just wondering if it's the 8TB or 16TB of virtual memory address
    > space that a 64bit processor can address on a 64bit Operating System
    > (Microsoft x64)? Is there any other Operating System in the market that
    > can address more than 16TB of virtual address memory that Microsoft
    > Windows x64 does? This is because 2^64 is 1.8447 x 10^19.
    >
    > Thanks
    > Hemanth
    >
    >
    > "Charlie Russel - MVP" wrote:
    >
    >> Well, as you point out, the RAM is directly addressable. But more than
    >> that, it can run 64-bit versions of software which can also directly
    >> address that RAM, and have access to 8TB of virtual memory address
    >> space. Finally, even 32-bit programs that are written to address memory
    >> >2GB will have access to a full 4GB of directly addressable virtual

    >> memory address space, instead of a maximum of 3GB (directly addressable)
    >> on 32-bit Windows.
    >>
    >> --
    >> Charlie.
    >> http://msmvps.com/xperts64
    >>
    >> bill wrote:
    >>> What are the advantages of an x64 OS vs. a Windows 2003 Enterprise
    >>> server if one has 32GB or less RAM?
    >>> (The Enterprise can address 32GB of RAM)
    >>>
    >>> I think the biggie is not just the amount of RAM but the x64 box can
    >>> address the memory as a single 64-bit offset (from a base register) and
    >>> doesn't need 32-bit workarounds like AWE.
    >>>
    >>> I also read that x64 CPU hardware stops certain types of "buffer
    >>> overrun" attacks that are possible with 32-bit CPU?
    >>>
    >>> Can you add any other items to this list.(or maybe correct my above
    >>> statements if they are wrong.)
    >>>
    >>>
    >>> TIA,
    >>>
    >>> Bill
    Charlie Russel - MVP, Mar 2, 2006
    #4
  5. Hemanth wrote:
    > I am just wondering if it's the 8TB or 16TB of virtual memory address space
    > that a 64bit processor can address on a 64bit Operating System (Microsoft
    > x64)? Is there any other Operating System in the market that can address more
    > than 16TB of virtual address memory that Microsoft Windows x64 does? This is
    > because 2^64 is 1.8447 x 10^19.


    Well noticed. As far as I understand, it is a limitation in the
    processor architecture. The virtual address is devided into several
    parts, which are then looked up in different layers of page tables. The
    format of a virtual address is as follows: 16bits are unused, 4 times 9
    bits are used for the four levels of page tables, and the lower 12 bits
    are directly used as an offset on the page base.

    Given that user mode programs never have to deal with this, this scheme
    could easily be extended to cover another page table level (or two).
    Only a small part of the kernel needs to be changed. But for now, AMD64
    only supports 48bit virtual addresses.

    Of course the physical address side is even "less complete". There are
    only 40 address lines, limiting the physical address space to 1TB at the
    moment. Not that anybody could afford that anyway :)

    Thomas
    Thomas Steffen, Mar 2, 2006
    #5
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