ASRock P4V88, DDR DIMM's

Discussion in 'Computer Information' started by mborgbusuttil@onvol.net, Mar 17, 2008.

  1. Guest

    My PC motherboard is an ASRock P4V88. I was using a DDR DIMM purchased
    last year(512Mb pc3200). This year I purchased 3 DDR DIMM's of the
    same brand and the same specifications and added them, however I could
    not set my motherboard to "dual channel". I am suspecting that
    although they have the same specifications as the one I bought last
    year they may not be entirely identical to it and the motherboard is
    detecting this difference. In fact their outward appearance is
    slightly different. Now my motherboards manual is saying that when all
    four memory banks are filled the DDR DIMM's have to be identical. Do I
    risk damaging my motherboard, or is it just an issue of stability?
     
    , Mar 17, 2008
    #1
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  2. Paul Guest

    wrote:
    > My PC motherboard is an ASRock P4V88. I was using a DDR DIMM purchased
    > last year(512Mb pc3200). This year I purchased 3 DDR DIMM's of the
    > same brand and the same specifications and added them, however I could
    > not set my motherboard to "dual channel". I am suspecting that
    > although they have the same specifications as the one I bought last
    > year they may not be entirely identical to it and the motherboard is
    > detecting this difference. In fact their outward appearance is
    > slightly different. Now my motherboards manual is saying that when all
    > four memory banks are filled the DDR DIMM's have to be identical. Do I
    > risk damaging my motherboard, or is it just an issue of stability?


    A motherboard has two options, when presented with non-matching
    DIMMs.

    1) Operate in virtual single channel mode. Each of the four DIMMs
    work, but are accessed only one at a time. As if the four
    DIMMs are sitting on a single channel. Operation will be
    stable, as it is designed to work that way (i.e. single channel
    operation is one of the options put in there by design).

    2) For chipsets which have "strict matching" policies, the
    non-matching stick may be ignored/rejected by the BIOS.
    For example, if I had a matched pair in A1-B1 and a
    mismatched pair in A2-B2, the A2-B2 ones may be ignored.

    In terms of matching, the parameters of interest are
    rows, columns, banks, ranks.

    Inside the memory chip, are the rows, columns, and banks.
    Some memory chips are quad bank, meaning the memory is
    logically partitioned into four chunks. The rectangular
    dimensions of each chunk, is "rows x columns".

    At the module level, they arrange memory chips, such that a
    64 bit wide memory array is constructed. For example, you
    could use 8 chips each 8 bits wide, to do it. If a DIMM
    had 16 chips total, of the 8 bit wide variety, then there
    are enough chips for "two ranks". That is popularly
    described as "double sided". Each rank is a 64 bit wide array.
    And the two ranks sit in parallel to one another.

    In recent years, some single sided 512MB DIMMs have become
    available. The majority (older ones) would be double sided
    512MB DIMMs. The chip density difference is a factor of 2,
    meaning the "rows x columns" on those two different kinds
    of DIMMs, will not be the same. That would be why the
    BIOS is not treating such a case, as dual channel.

    A single sided 512MB, is not the same as a double sided 512MB.
    The single sided would have a total of 8 chips, the
    double sided a total of 16 chips (assuming no ECC).

    The user manual usually has some hints, about whether the
    chipset is (1) or (2). But the feedback you're getting
    from the BIOS, as to whether all four are matched, would
    also be a clue.

    http://download.asrock.com/manual/P4V88.pdf

    There is no risk of damage, as they are all DDR DIMMs,
    have the same voltage ratings, the same signal names.
    Pin compatible in other words. The result, might be
    slightly less performance or less total memory, than
    you would otherwise expect. Annoying but no damage.

    Buying a fourth, to match the other three, would be
    a possible solution. But even so, there are no
    guarantees in life, when it comes to BIOS design.
    Sometimes, an early BIOS, will have bugs with respect
    to memory configuration, and the BIOS might still
    complain. So while you can do your best to match them,
    there is still a chance of some odd behavior. In
    that regard, Googling for previous experience or
    looking in private forums, is one way to discover
    how the thing works or doesn't work.

    Paul
     
    Paul, Mar 17, 2008
    #2
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  3. Guest

    On Mar 17, 8:43 pm, Paul <> wrote:
    > wrote:
    > > My PC motherboard is an ASRock P4V88. I was using a DDR DIMM purchased
    > > last year(512Mb pc3200). This year I purchased 3 DDR DIMM's of the
    > > same brand and the same specifications and added them, however I could
    > > not set my motherboard to "dual channel". I am suspecting that
    > > although they have the same specifications as the one I bought last
    > > year they may not be entirely identical to it and the motherboard is
    > > detecting this difference. In fact their outward appearance is
    > > slightly different. Now my motherboards manual is saying that when all
    > > four memory banks are filled the DDR DIMM's have to be identical. Do I
    > > risk damaging my motherboard, or is it just an issue of stability?

    >
    > A motherboard has two options, when presented with non-matching
    > DIMMs.
    >
    > 1) Operate in virtual single channel mode. Each of the four DIMMs
    >     work, but are accessed only one at a time. As if the four
    >     DIMMs are sitting on a single channel. Operation will be
    >     stable, as it is designed to work that way (i.e. single channel
    >     operation is one of the options put in there by design).
    >
    > 2) For chipsets which have "strict matching" policies, the
    >     non-matching stick may be ignored/rejected by the BIOS.
    >     For example, if I had a matched pair in A1-B1 and a
    >     mismatched pair in A2-B2, the A2-B2 ones may be ignored.
    >
    > In terms of matching, the parameters of interest are
    > rows, columns, banks, ranks.
    >
    > Inside the memory chip, are the rows, columns, and banks.
    > Some memory chips are quad bank, meaning the memory is
    > logically partitioned into four chunks. The rectangular
    > dimensions of each chunk, is "rows x columns".
    >
    > At the module level, they arrange memory chips, such that a
    > 64 bit wide memory array is constructed. For example, you
    > could use 8 chips each 8 bits wide, to do it. If a DIMM
    > had 16 chips total, of the 8 bit wide variety, then there
    > are enough chips for "two ranks". That is popularly
    > described as "double sided". Each rank is a 64 bit wide array.
    > And the two ranks sit in parallel to one another.
    >
    > In recent years, some single sided 512MB DIMMs have become
    > available. The majority (older ones) would be double sided
    > 512MB DIMMs. The chip density difference is a factor of 2,
    > meaning the "rows x columns" on those two different kinds
    > of DIMMs, will not be the same. That would be why the
    > BIOS is not treating such a case, as dual channel.
    >
    > A single sided 512MB, is not the same as a double sided 512MB.
    > The single sided would have a total of 8 chips, the
    > double sided a total of 16 chips (assuming no ECC).
    >
    > The user manual usually has some hints, about whether the
    > chipset is (1) or (2). But the feedback you're getting
    > from the BIOS, as to whether all four are matched, would
    > also be a clue.
    >
    > http://download.asrock.com/manual/P4V88.pdf
    >
    > There is no risk of damage, as they are all DDR DIMMs,
    > have the same voltage ratings, the same signal names.
    > Pin compatible in other words. The result, might be
    > slightly less performance or less total memory, than
    > you would otherwise expect. Annoying but no damage.
    >
    > Buying a fourth, to match the other three, would be
    > a possible solution. But even so, there are no
    > guarantees in life, when it comes to BIOS design.
    > Sometimes, an early BIOS, will have bugs with respect
    > to memory configuration, and the BIOS might still
    > complain. So while you can do your best to match them,
    > there is still a chance of some odd behavior. In
    > that regard, Googling for previous experience or
    > looking in private forums, is one way to discover
    > how the thing works or doesn't work.
    >
    >     Paul


    Thanks Paul for a very clear explanation. Youv'e put my mind at rest.
     
    , Mar 18, 2008
    #3
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