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Answermemory usage/allocation

  • Tuesday, March 24, 2009 9:32 AMickymay Users MedalsUsers MedalsUsers MedalsUsers MedalsUsers Medals
     
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    I have noticed that my RAM which is being recognized in my 64bit version of win7 is being seen by the system but there is only a percentage of it stated as free for system use, I would assume that this means some is dedicated to running my  system and this includes my graphics card ?

    I ran a dxdiag to look at what was going where

    [quote]Display Devices
    ---------------
      Card name: NVIDIA GeForce 9800 GTX/9800 GTX+ (Prerelease - WDDM 1.1)
      Manufacturer: NVIDIA
      Chip type: GeForce 9800 GTX/9800 GTX+
      DAC type: Integrated RAMDAC
      Device Key: Enum\PCI\VEN_10DE&DEV_0612&SUBSYS_059210DE&REV_A2
      Display Memory: 2289 MB
      Dedicated Memory: 497 MB
      Shared Memory: 1791 MB[/quote]

     now if I understand this right, with my graphics card which has 512mb of onboard DDR2 memory, win7 has still allocated 1791 MB as shared memory giving me a total of 2289 MB for my graphics display 

    can anyone explain why this is and how it works and how it might make choosing a graphics card for your system also directly affect your available RAM ?

    N.B. is this something similar or actually PAE in 64 bit ?

     

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  • Tuesday, March 24, 2009 12:24 PMMark L. FergusonMVP, ModeratorUsers MedalsUsers MedalsUsers MedalsUsers MedalsUsers Medals
     
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    Yes, that is exactly how it works. Running Win 7 and Aero will take a lot of video ram.
    Rating posts helps other users
    Mark L. Ferguson MS-MVP
     
  • Tuesday, March 24, 2009 8:42 PMickymay Users MedalsUsers MedalsUsers MedalsUsers MedalsUsers Medals
     
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    but why have a dog then bark myself ?

    If i decided to by a gfx card with say 1gig onboard this will leave windows mirroring the same ammount allocated from my system RAM , doesn't that defeat the object of buying gfx cards with larger and larger onboard memory ?
     
  • Tuesday, March 24, 2009 9:00 PMusasmaMVP, AnswererUsers MedalsUsers MedalsUsers MedalsUsers MedalsUsers Medals
     
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    No, as it reduces the load that Windows has to take up.  Also, that shared memory is (as I recall) dynamically allocated - so the numbers can change on the fly.

    FWIW - dxdiag reports from my system:
    Display Devices
    ---------------
            Card name: ATI Radeon HD 4800 Series (Microsoft Corporation WDDM 1.1)
         Manufacturer: ATI Technologies Inc.
            Chip type:
             DAC type: Internal DAC(400MHz)
           Device Key: Enum\PCI\VEN_1002&DEV_9440&SUBSYS_E850174B&REV_00
       Display Memory: 3571 MB
     Dedicated Memory: 503 MB
        Shared Memory: 3067 MB

    And I'm surely not using 3571 MB of video memory with only a couple of apps open.
    But, as I've got 12 gB of RAM, I'm sure that the video is using that much just because it can - not because of any need to use it.
    - John
     
  • Tuesday, March 24, 2009 9:38 PMusasmaMVP, AnswererUsers MedalsUsers MedalsUsers MedalsUsers MedalsUsers Medals
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    To further clarify this, here's a link to an MSDN blog that may explain it better:  Zemblanity's blog
    - John
    • Marked As Answer byickymay Tuesday, March 24, 2009 10:13 PM
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  • Tuesday, March 24, 2009 10:13 PMickymay Users MedalsUsers MedalsUsers MedalsUsers MedalsUsers Medals
     
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    thnx for the link that explains it, or more to the point the white paper he points to http://www.microsoft.com/whdc/device/display/graphicsmemory.mspx the "graphics memory.doc" over on the right , It is all about the new implimentation of "WDDM" or Windows (Vista) Display Driver Model.

    It is refreshing that it's dynamic as an important part of DX10 coping with Aero amongst other things , a resource heavy graphical interface ?