Quick Q .. 32bit v 64bit (2003) system memory space

Discussion in 'Windows 64bit' started by NuTCrAcKeR, Aug 30, 2006.

  1. NuTCrAcKeR

    NuTCrAcKeR Guest

    Hello All,

    This may have been asked before, but I searched the postings and did not
    find what i was looking for.

    In the 32bit world, the OS gets 2GB of ram, and then the rest of the memory
    is diced up into 2GB chunks for applications. This can be changed from 2/2
    to 1/3 when using 4GT.

    Now, under 2003 x64, does that same rule hold true? Is there a limited
    amount of " OS Memeory " space that is reserved for system operations, and
    the rest is available for applications (like SQL and Exchange) ?

    The end I am trying to reach is whether an IIS, or File and Print, server
    would actually benefit from more than 2GB of ram.


    - NuTs
    NuTCrAcKeR, Aug 30, 2006
    1. Advertisements

  2. Well and thoroughly covered on the 64bit pages at microsoft.com, but the
    short answer is that in x64 user processes have 8TB of memory address space
    available to 64bit applications. The OS has 8TB as well.

    Note that RAM and Address Space are NOT the same, and you're not strictly
    correct as you described 32-bit. Also note that in x64 Edition, applications
    which are written to take advantage of >2GB of memory address space will
    automatically get a full 4GB of memory address space - no switch required.
    Ordinary applications, which could NOT take advantage of this extra memory
    address space in 32-bit Windows will still not be able to.
    Charlie Russel - MVP, Aug 30, 2006
    1. Advertisements

  3. NuTCrAcKeR

    NuTCrAcKeR Guest

    thanks for that. Now, to specifically answer my question, if a box has 4 or
    8 GB of ram, will IIS worker process spaces (aspnet_wp, etc) be able to
    address and use all 4GB/8GB, for say webgardens, on x64? On 32bit systems,
    such working memory spaces would be limited to 2GB because they operate in
    the OS address spaces.


    - NuTs
    NuTCrAcKeR, Aug 30, 2006
  4. If IIS is running as 32-bit, then it will see 4GB of Virtual Memory Address
    space. That's all 32bit apps can see. If it's running as a 64bit app, then
    it will see 8TB of Virtual Memory Address space. How Virtual Memory Address
    space relates to RAM is a somewhat different issue, but the short answer for
    your purposes is that it will behave as if it can see all that RAM if it's
    64bit, and 4GB if it's 32bit.
    Charlie Russel - MVP, Aug 30, 2006
  5. NuTCrAcKeR

    NuTCrAcKeR Guest

    I was under the impression that IIS isnt run as an application, per se, and
    therefore can only get its hooks into 2GB of that windows core memory. The
    MS support site even cautions about turning on 4GT when using IIS ... why
    else would that be?
    NuTCrAcKeR, Aug 31, 2006
  6. NuTCrAcKeR

    Admiral Q Guest

    Depending on mode (x86 or x64) IIS has access to 4GB or 8TB, where you keep
    coming up with 4GT is beyond me?
    Admiral Q, Aug 31, 2006
  7. NuTCrAcKeR

    NuTCrAcKeR Guest

    when i say 4GT, im talking about 4 Gigabyte RAM Tuning ... utilizing the
    /3GB switches in the boot.ini. (among other methods)

    Why is 4GT significant? because in a box with 4GB of ram, windows will take
    2GB (Kernal Memory)and then start giving applications thier own memory, up
    to 2GB (virtual) each. This is strictly a 32bit convnetion. When you use
    4GT, you limit the Kernel to 1GB of physical memory, there by increasing
    application memory by 50% to 3GB instead of 2 (and each application gets 2GB
    of virtual memory that is mapped to the physical memory on the box).


    I know that 4GT only applies to 32bit systems, and with everyones help I
    have come to understand that up to 8TB of ram can be addressed (virtually)
    by each 64bit process (which i would imagine IIS would be).


    now, the question is when a system is built with 8GB of ram, how much is
    reserved for Kernel memory, and how much is reserved for applications?


    - NuTs
    NuTCrAcKeR, Aug 31, 2006
  8. The reason MS support cautions you about turning on the /3GB switch is
    because it will make the situation worse. The problem with running /3GB is
    that it starves the OS. This makes the OS far more vulnerable to a DOS
    attack, for example, or just too many legitimate connections.

    Take a look at the deployment scenarios whitepaper I wrote for the launch of
    x64. http://www.microsoft.com/windowsserver2003/64bit/x64/deploy.mspx

    In x64 edition, you get the benefits of /3GB (actually, you get 4GB) without
    the penalty of starving the OS.
    Charlie Russel - MVP, Aug 31, 2006
  9. NuTCrAcKeR

    Bo Persson Guest

    It isn't the RAM that is reserved, it is the address space.

    On a 4 GB 32 bit system, the virtual address space is the same size as
    the physical space. That makes the virtual addressing much less
    useful, as you will run out of *virtual* addresses.

    On a 64 bit system, you have 8 TB of virtual addresses that can be
    mapped to your 8 GB of RAM, as needed. The parts that doesn't fit will
    be swapped to disk. No problem.

    Bo Persson
    Bo Persson, Aug 31, 2006
  10. NuTCrAcKeR

    NuTCrAcKeR Guest

    Excellent white paper. It clarified several misconceptions for me. This is
    definitely something I can use.

    Thank you very, very much !

    - NuTs
    NuTCrAcKeR, Aug 31, 2006
  11. Why thank you. There are several whitepapers out there on x64, both client
    and server, that I have written. This was actually the very first.
    Charlie Russel - MVP, Aug 31, 2006
  12. The disconnect between address space and RAM is a very common misconception.
    I suspect we'll see the same misconception when our PC's have 16 TB of RAM.
    ;) (and yes, I hope and expect to live that long!)
    Charlie Russel - MVP, Aug 31, 2006
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.