Win 7 64Bit install. 4GB RAM showing as (3.50GB usable)

Discussion in 'Windows 64bit' started by Alan Kent, Sep 1, 2009.

  1. Alan Kent

    Alan Kent Guest

    Hi All

    I have successfully installed my MSDN 64Bit version of Windows 7 Ultimate on
    a DELL Dimension 9100 PC.

    The problem I am having is with the RAM. The PC has 4GB of ram that shows up
    fine within the BIOS. When I go into the Windows 7 System Control Panel it
    shows as 4.00GB (3.50 usable). I can understand this will happen with a
    32bit operating system, but this is a new install of the 64bit version of
    Windows 7 Ultimate. I have the latest BIOS version installed. My system spec
    is as follows:

    DELL Dimension 9100
    Intell(R) Pentium(R) D CPU 2.80GHz 2.79GHz / Dual Processor
    64Bit (Intel EM64T)
    4 x 1GB DDR2 SDRAM

    When I use the full 4GB the 7 System Control Panel shows as 4.00GB (3.50
    usable).
    When I remove 2GB the 7 System Control Panel shows as 2.00GB.

    Is this a bug, and if so is there a workaround? Maybe this is normal and
    should happen.

    Please help
    Alan
     
    Alan Kent, Sep 1, 2009
    #1
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  2. I don't think it's a bug, I think it's the limitations of the hardware.
    According to the Dell documentation your hardware limit is 4GB. The
    1/2GB lost may be taken up by the motherboard or assigned to the video,
    or any number of reasons. I think you're just going to have to live
    with what you've got.
     
    Bobby Johnson, Sep 1, 2009
    #2
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  3. To have all 4GB available to use you would have to find and enable a
    Memory Remap setting in the BIOS. But I think the Dimension 9100 was
    only sold with XP, a 32-bit OS, so the setting probably does not exist
    even though the hardware is capable of using all 4GB.
     
    Dominic Payer, Sep 1, 2009
    #3
  4. Alan Kent

    Tom Ferguson Guest

    Tom Ferguson, Sep 1, 2009
    #4
  5. Alan Kent

    Jerry Guest

    If he really has a 32-bit only motherboard and cpu then how did he install
    Win7 64-bit?
     
    Jerry, Sep 1, 2009
    #5
  6. Alan Kent

    dennis Guest

    Because the CPU supports 64bit, but the motherbord/chipset only has a
    32bit address bus. Also, 32bit CPUs have supported 36bit addressing for
    years, but that doesn't mean all boards supports it.
     
    dennis, Sep 2, 2009
    #6
  7. Alan Kent

    Wonderman Guest

    I have almost the exact same system specs in a Sony wuth the same chipset
    running Vista 64. Where are you seeing the lower memory number ?
     
    Wonderman, Sep 2, 2009
    #7
  8. Alan Kent

    Ian D Guest

    The 945 Lakeport chipset does not support memory remapping.
    It will take a 64 bit CPU, and run a 64 bit OS, as the data bus is
    64 bits.
     
    Ian D, Sep 3, 2009
    #8
  9. Alan Kent

    Curious Guest

    He does not have a 32bit motherboard he has a motherboard which will support
    64 bit CPUs but which will not support more then 4MB of installed memory.
     
    Curious, Sep 3, 2009
    #9
  10. Alan Kent

    Al Dykes Guest


    Can I leap to the conslusion that if HP puts 6GB of RAM in a cheap
    desktop and ships it with a 64 bit OS, the system is fully 64-bit
    datapaths?

    (Even video, which in this case is on-mobo in the G33 coprocessor
    chip.)
     
    Al Dykes, Sep 3, 2009
    #10
  11. Alan Kent

    Curious Guest

    Yes all 64 bit applications and drivers will use 64 bit datapaths.
    Older 32 bit applications will continue to use 32 bit data paths.
     
    Curious, Sep 3, 2009
    #11
  12. Alan Kent

    Ian D Guest

    Yes, but the amount of memory has nothing to do with
    it. Even if there is only 1GB, the data bus width is still
    64 bits.

    The data bus became 64 bit with the introduction of the
    Pentium back in 1993. Even a 32 bit OS makes full use of
    the 64 bit data bus. The 64 bit data width allows two 32
    bit instructions to be accessed simultaneously. This
    increases CPU efficiency by allowing two instructions to
    be processed in a single memory access cycle.
     
    Ian D, Sep 3, 2009
    #12
  13. Alan Kent

    Curious Guest

    AFAIK the 64 bit compiler supports the creation of a single 64 bit
    instruction that can combine 2 32 bit instructions.
    If is not my understanding that a 64 bit OS automatically combines two 32
    bit instructions into one 64 bit instruction. If it did then 32 bit
    applications would not run slightly slower when being run a 64bit OS in
    32bit emulation mode.
     
    Curious, Sep 3, 2009
    #13
  14. Alan Kent

    Ian D Guest

    I didn't say that a 64 bit OS combines two 32 bit instructions.

    What I said was that the 64 bit data bus, which was introduced
    with the Pentium, allows a 32 bit OS to make full use of the
    64 bit data path by simultaneously accessing two 32 bit
    instructions, side by side, in a single memory access cycle.
     
    Ian D, Sep 4, 2009
    #14
  15. Alan Kent

    Curious Guest

    And what I said was that a 64 bit OS can not combine 2 instructions
    contained in a 32 bit application and execute them in one cycle in a 64 bit
    OS.
    You are confusing the issues between the use of 64 bit compilers to execute
    64 bit instructions and the ability of 32 bit applications to address more
    then 4MB of address space which they can not do since the only use 32 bit
    memory addresses.
     
    Curious, Sep 4, 2009
    #15
  16. While this article is aimed at game developers, it does explain the memory
    issues around 4 GB in detail. You might find it useful:

    http://www.gamasutra.com/view/feature/3602/sponsored_feature_ram_vram_and_.php

    Standard 32-bit applications run exactly the same on a x64 CPU and 64-bit
    version of Windows as they would on a standard version of Windows. The main
    difference is that the OS itself can utilize extra memory for multitasking.
    Some specially enabled 32-bit applications can make use of some extended
    memory beyond what it could on a 32-bit version of the OS. The main point of
    x64 technology is that 32-bit applications just work while enabling new
    classes of applications.

    x64 native applications are compiled with x64 specific instructions and
    assumptions. If you are interested in the technical details , see:

    DirectX Technical Article - 64-bit programming for Game Developers
    http://msdn.microsoft.com/en-us/library/bb147385(VS.85).aspx

    or the Gamefest 2008 presentation:
    http://www.microsoft.com/downloads/...6A-EE8A-406A-A5AE-9E065343CD06&displaylang=en
     
    Chuck Walbourn [MSFT], Sep 4, 2009
    #16
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