A7V880 - 4x1GB DDR400 Unbuffered Modules...Is it possible?

Discussion in 'Asus' started by News su Libero, Apr 10, 2005.

  1. Please help me...
    I'd like to know if is possible to install 4x1GB DDR400 Unbeffered Modules on Asus A7V880...
    4GB of ram can be recognized or ONLY buffered/registered modules are needed?
    How Kingston DDR- PC3200 1GB Modules works on this motherboard?

    Any experience or suggestion will be appreciated.
    I need to work with a 4GB Computer (I'm a CAD Designer)

    News su Libero, Apr 10, 2005
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  2. News su Libero

    Hulttio Guest

    according to manual you can use 4GB of regular memory.
    buffered/registered memory is not supported.
    Hulttio, Apr 10, 2005
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  3. News su Libero

    Paul Guest

    If you look at the QVL (qualified vendor list) of memory modules
    for this board, some Transcend 1GB modules have been tested.
    Apparently, four modules of the 1GB size work.

    Soyo makes a KT880 motherboard as well, and their manual says:

    "The largest memory capacity possible is 4GB. On this
    motherboard, DRAM speed can be set independent from the CPU
    front side bus speed. Note that when installing 4GB of memory,
    your total memory will be less than 4GB. The reason for this is
    that the BIOS, PCI and AGP cards claim part of your CPUs address

    That means, if you install 4x1GB, the motherboard will report there
    is 3.2GB or so of memory installed. 800MB is thrown away, to leave
    room in the memory map for access to the PCI and AGP cards.

    In terms of memory type, the board uses unbuffered memory modules
    (so no registered modules). 1GB modules will be more expensive than
    two 512MB modules, so be prepared for a fairly expensive computer.

    1GB modules start at $73 on pricewatch.com . These cheap modules
    are likely stacked construction, which I do not recommend that
    you buy. The kind of modules you should be using, should have
    (16) 64Megx8bit chips. 64Mx8 chips are more expensive than the
    128Mx4 chips you are likely to find on these $73 modules. You
    can always phone these vendors and see if the construction is
    correct or not. If you can get a money back guarantee, then
    try them out.


    The cheapest valid construction I can see is some Samsung
    M368L2923BTM-CCC for $104 (page 3 of the pricewatch list).
    From the Samsung web site, they use 64Mx8 chips and are
    3-3-3 timing.


    In terms of brand name memory, the best memory you can find is
    TWINX2048-3200C2 2.5-3-3-6 memory, at $325 a pair. Or maybe some
    OCZ OCZ4001024ELPE 2-3-2-5 memory at $242 _each_. There is a big
    difference between premium memory, and that Samsung stick.

    Now, the other side of the coin, is can the application actually
    use the 3.2GB or so of memory you have got:

    1) The application must be compiled to work with larger memory.
    Possibly 2GB max without compiler flag. 3GB max with compiler
    flag. On a server OS capable of handling more than 4GB memory,
    a single process cannot have more than 4GB (possibly 64 bit
    OS + 64 bit application will fix this). Or something like
    that... Things get tricky near 4GB or higher.

    2) The OS you use sets a limit to the amount of memory. The kernel
    needs its own memory space, and the user space gets the rest.
    There are flags that can be used in boot.ini for this:


    3) When using a Northbridge that has the memory controller in
    it, some address space must be reserved for PCI/AGP/PCI-Express
    busses. If you insert 4GB of memory in the machine, the Northbridge
    will only allow 3+ GB of the memory to be used, and the rest of
    the memory is "thrown away" to prevent a conflict with the
    address space used by the busses. The best you can do in a
    situation like this, might be to use a PCI video card, to reduce
    the wasted address space - then you have disabled the AGP slot.
    (With two PCI Express video cards present in a board like the
    A8N-SLI, 4GB of memory results in only 2.75GB being usable, due
    to the address space issue. There is more info on Athlon64 below.
    Some of the Intel chipsets have a rough limit of around 3.2GB
    usable. Googling may yield some user experience on this.)

    4) If you buy an Athlon64 board or an Opteron based board,
    the memory controller is inside the processor. The processor
    supports a 64 bit world, and via a memory mapping function called
    "memory hoisting", it is possible to avoid the problem in (3).
    But if you purchase an Athlon64 board (like a socket 939 board),
    you will also need an OS that can handle larger than 32 bit
    address space. (I.e. Plan for 5GB worth of address space, to
    be able to make use of 4GB of memory.) Some Intel server chipsets
    support memory hoisting (remapping) too.

    The Athlon64 has MMIO, to allow 32 bit PCI cards to access
    a window into 64 bit processor memory. Intel is missing this
    feature, at least on desktop processors - 32 bit PCI I/O data
    must be manually copied to an address space higher than 4GB,
    as I understand it. This is what happens when not all of the
    hardware in a computer is 64 bit ready. While a 64 bit processor
    and supporting motherboard make your quest a tiny bit easier,
    it will still be a struggle on the software side.

    In other words, support for large memory spaces is problematic,
    and requires money and methodical removal of barriers to success.
    Any noob (like me) can get a 2GB system running, but only a
    genius will get to see the full usage of 4GB of memory inside
    their CAD application.

    You could also have a look at the Microsoft Knowledgebase, for
    articles relating to large memory:


    "Large memory support is available in Windows 2000 and Windows Server 2003"

    You have a bit of research ahead of you.

    Your most likely solution, is to use the /3GB switch, use a server
    OS, and make sure the CAD software has been compiled for at least
    3GB operation. If you are lucky, the slightly more than 3GB you
    will get on the A7V880 will be usable.

    One thing you can look forward to, is you can reuse those 1GB
    unbuffered DDR400 modules in an Athlon64 S939 motherboard later.
    On the Asus motherboards, memory hoisting was added as an
    afterthough in the BIOS, so you won't see the memory hoisting
    setting in the downloadable motherboard manuals for most S939

    Memory hoisting on Athlon64 is very briefly explained on page 90
    here if you are interested. This discusses the handling of the
    I/O hole just below the 4GB mark, and how system memory is broken
    into two pieces physically, yet in the virtual address space
    looks contiguous. I.e. low_memory, I/O_hole, high_memory

    This Google posting makes a nice reference:

    Another alternative is to go with a dual Opteron board and some
    registered memory for the Opterons. Much more elbow room, if you
    are serious about >4GB memory. If your software only uses one
    processor, no problem, as the second Opteron functions as the
    Northbridge to the second array of memory DIMMs.

    Have fun,
    Paul, Apr 11, 2005
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