Re: RAM

Discussion in 'Computer Information' started by Paul, May 2, 2009.

  1. Paul

    Paul Guest

    Van Chocstraw wrote:
    > Why would a motherboard be limited to 2 gig of ram? What happens if you
    > put in 4 gig?


    Some memory limitations -

    *******
    The first way, is limited by

    number_of_slots * max_address_per_slot

    Take my Nforce2 motherboard for example. The addressing works
    up to 1GB per slot. That would be some multiplexed row * column
    address. There are only enough address bits in the RAM slot,
    to handle 1GB made from x8 width chips. If a 2GB stick of memory
    was used, or a high density 1GB x4 DDR stick was used, only
    half the memory is detected. So that is addressing at the
    slot level.

    *******
    The second way, is an artificial limitation by the chipset manufacturer.
    Intel made a chipset, where the system max for memory was 512MB.
    But each of three slots could address 512MB. The customer was
    robbed of the ability to install 1.5GB of memory, because Intel
    wanted to force them to use another product. In this case,
    the address map had limitations, but the limitations are imposed
    internally inside the chipset. Additional memory would be
    ignored during BIOS setup, because the internal limitation
    would prevent the BIOS from using it.

    *******
    The third way, can be by means of the interconnect between the
    Northbridge and the processor. Some chipsets were made, where
    the FSB address bus is 32 bits, while other, more modern chipsets
    have at least a 36 bit bus.

    The chipset in question, had four slots, each capable of addressing
    2GB. In theory, you should have been able to install 8GB of memory.
    But due to the front side bus connection not having enough
    address bits, the upper limit is 4GB (minus I/O space requirements).

    *******
    The fourth way, is via BIOS stupidity. I have a motherboard,
    where there are only two slots. Since DDR2 is used, you can
    easily find 1GB or 2GB sticks for sale. If you install two
    2GB sticks, the motherboard is not stable. So I can install
    the 4GB, it is seen by the OS, but the machine is not stable
    enough to use.

    The manufacturer didn't want to do any development work on the
    BIOS, so a number of features are missing. Including proper
    "tuning" for the differences between 1GB and 2GB sticks.
    Thus, they list 1GB sticks as the biggest it supports.

    There are probably other ways, but those are some that
    come to mind.

    You can always plug in the larger sticks, and just see what
    happens. It shouldn't damage anything, and would only end
    up being a waste of money if it doesn't work. I have 2x2GB
    sitting in my junk pile right now, waiting for the day when
    I have a proper motherboard.

    HTH,
    Paul
    Paul, May 2, 2009
    #1
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  2. "Paul" <> wrote in message
    news:gthj88$f0m$...
    >
    > You can always plug in the larger sticks, and just see what
    > happens. It shouldn't damage anything, and would only end
    > up being a waste of money if it doesn't work.


    <snip>

    I have 2x2GB
    > sitting in my junk pile right now, waiting for the day when
    > I have a proper motherboard.
    >
    > HTH,
    > Paul


    I bought just such a motherboard the other day for $50 at Fry's. I also
    bought 2x2G of RAM for $50, with a $25 rebate (making the cost of the RAM
    $25).

    A "proper" motherboard is just a keystroke away ...
    Jeff Strickland, May 2, 2009
    #2
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