What is the differance in single and double sided memory.

Discussion in 'Asus' started by SPAWN, Dec 10, 2004.

  1. SPAWN

    SPAWN Guest

    How do you tell them apart?,i know this is a newbie question,but i would
    like to know,thanks for any info
     
    SPAWN, Dec 10, 2004
    #1
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  2. SPAWN

    Tod Guest

    Single sided has memory chips on only one side of the DIMM.
    Double sided has memory on both sides of the DIMM.
     
    Tod, Dec 10, 2004
    #2
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  3. SPAWN

    SPAWN Guest

    Thats what i thought,My board is an Asus K8V-SE DELUXE and i was just
    woundering about the chips,i have 2 512 chips that a single and a 256 chip
    that is also single,but according to my owners manual,it does not say
    anything about three chips of DDR3200 single sided,only for the 333mhz,not
    the 400MHZ.
     
    SPAWN, Dec 10, 2004
    #3
  4. SPAWN

    Paul Guest

    Here are some DIMM configurations. This one is a single rank DIMM
    that uses only four chips.

    0..15 16..23 24..47 48..63
    | | | |
    --- --- --- --- Single rank 64bit wide memory
    | | | | | | | | using x16 chips.
    | | | | | | | |
    | | | | | | | |
    --- --- --- ---
    | | | |
    When the next DIMM is laid out, all eight chips could be
    placed on the same side of the DIMM (means only one pass through
    the soldering line). But, electrically, if four are placed on
    each side of the board, the data bus connections can be made a
    bit shorter, so you might see this as two sides of four chips.
    In terms of "sided-ness", these same eight chips could be
    described as single sided or double sided. But the DIMM
    would always be "dual rank", as it has two logical banks
    of memory. That is why "sided-ness" is not a precise term
    and is a poor way to rate loading.

    00..15 16..23 24..47 48..63 00..15 16..23 24..47 48..63 MDATA
    | | | | | | | |
    --- --- --- --- --- --- --- --- Dual rank
    | | | | | | | | | | | | | | | | 64bit wide
    | | | | | | | | | | | | | | | | using x16
    | | | | | | | | | | | | | | | | chips
    --- --- --- --- --- --- --- ---
    | | | | | | | |
    A single rank 256MB DIMM can be constructed with some x8 chips.
    It takes eight chips to make a 64 bit wide memory, which is the
    normal width of DDR memory busses.

    00..07 08..15 16..23 24..31 32..39 40..47 48..55 56..63 MDATA
    | | | | | | | |
    --- --- --- --- --- --- --- --- Single rank
    | | | | | | | | | | | | | | | | 64bit wide
    | | | | | | | | | | | | | | | | using x8
    | | | | | | | | | | | | | | | | chips
    --- --- --- --- --- --- --- ---
    | | | | | | | |
    A dual rank 512MB DIMM is just a second instance of the array
    directly above.

    00..07 08..15 16..23 24..31 32..39 40..47 48..55 56..63 MDATA
    | | | | | | | |
    --- --- --- --- --- --- --- ---
    | | | | | | | | | | | | | | | | Two ranks
    | | | | | | | | | | | | | | | | 64bit wide
    | | | | | | | | | | | | | | | | using x8
    --- --- --- --- --- --- --- --- chips
    | | | | | | | |
    | MADDR
    +------+------+------+------+------+------+------+-+
    | | | | | | | |
    --- --- --- --- --- --- --- ---
    | | | | | | | | | | | | | | | |
    | | | | | | | | | | | | | | | |
    | | | | | | | | | | | | | | | |
    --- --- --- --- --- --- --- ---
    | | | | | | | |
    00..07 08..15 16..23 24..31 32..39 40..47 48..55 56..63 MDATA

    The reason there are speed limits in the table, is because of
    the number of address loads on the MADDR bus. A 16 chip DIMM
    is twice as bad as an 8 chip DIMM, and the tables are probably
    assuming the use of 8 or 16 chip DIMMs.

    Really, the config

    16chip, No_DIMM, 16chip

    should have the same loading as

    16chip, 8_chip, 8_chip

    so it too should be rated for DDR400.

    There is a slight electrical penalty from using more PCBs
    to mount the chips, as the extra substrate is another stub
    on the bus, so that will degrade the signal quality a bit.
    The compensating factor, is the two 8_chip loads are spaced
    apart a bit, which gives better distributed capacitance and
    less impedance drop. Those two factors should roughly cancel
    out, and the two configurations above should be equal.

    The S754 Athlon64 has two address busses. One bus drives slot1
    and the second bus drives slot2 and slot3. That is why the
    memory table has a slight preference for putting more load
    (i.e. a 16 chip DIMM) in slot1. The way the address busses are
    designed, one bus contains the inverse of the content of the
    second bus. When the electrical signals move in opposite
    directions, it helps balance the switching noise
    on the processor silicon die. Since only one DIMM pays attention
    to the value driven on the address bus at any given moment, it
    is OK for one bus to be driven with an invalid address, and
    that is how one address bus can be the inverse of the other.

    The address loading issue, is why you'll find the overclocking
    fraternity using a single DIMM on a memory channel, as that
    offers the least loading. You'll also see people using 256MB
    single rank DIMMs, to try to achieve the highest possible
    operating frequency ("clock rate is king").

    The way to rate the DIMMs, is by how many chips they have.
    An eight chip DIMM, whether it is a 2 x 4 chip DIMM or a 1 x 8
    chip DIMM, offers the same eight chip load on the address bus,
    and the penalty for those DIMMs is the same. The 2 x 8 DIMM
    is twice the load of either of those DIMMs.

    There are some other DIMM configurations, such as when shopping
    for 1GB DIMMs, you can find 1 x 16 chip DIMMs, where each chip
    is four bits wide. That is not a JEDEC approved configuration
    and Intel doesn't officially support it. There are also modules
    that used "stacked" chips, where there are actually two silicon
    die inside the same plastic packaged chip. A module like that
    can offer 32 loads to the address bus, and that is generally a
    recipe for disaster, as few busses can drive those kinds of
    modules with decent timing.

    When a stacked DIMM contains registers (a registered DDR DIMM),
    the register chip separates the memory chips from the memory
    bus, and that reduces the load immensely (the address bus
    drives a single register chip on each DIMM, hardly any load
    at all). And, that is why you'll find so many DIMM slots on a
    server board, because the board uses the easy to drive registered
    modules.

    If you look at the connections of the data bus bits, there are
    fewer loads to deal with. For example, if three dual rank DIMMs
    are placed on your motherboard, there are just six loads on a
    single data bus signal. It is much easier to drive that load,
    than to drive sixteen or thirty two address loads.

    If your three DIMMs only have eight or fewer chips per DIMM,
    there is a real good chance they'll work at DDR400. If slot 2
    plus slot 3 have more than a total of 16 chips, then DDR333
    or slower will be the result. As far as I can tell, the AMD
    provided table that Asus has copied into the manual, is
    slightly more pessimistic than it has to be.

    Good luck,
    Paul
     
    Paul, Dec 10, 2004
    #4
  5. That isn't entirely true, you can have a module that has 16 chips on it
    (both sides) and still be considered a "single-sided" module. It
    basically ends up referring to the number of electrical loads the module
    places on the memory bus..
     
    Robert Hancock, Dec 11, 2004
    #5
  6. SPAWN

    Mike Guest

    Thats what i thought,My board is an Asus K8V-SE DELUXE and i was just
    I've just checked my K8V-SE- D/X manual and it will take 3 x single sticks,
    however when 3 sticks are inserted the speed they run at is 333 not the normal
    400 which 2 sticks would use. This is common on many motherboards, ie. more
    memory runs a tad slower, but no doubt the extra memory offsets this.

    I note for example that the new large 1 gig sticks only support cas4 where the
    smaller decent quality memory sticks can go down to cas2.

    I've been considering adding another 512megs to my current 2x512megs myself but
    didn't like the idea that it would reduce the memory speed to 333.

    So the question is? Would one gain anything in extra smoothness in games etc
    which would offset the slightly lower memory speed, based on previous boards IME
    its not made a lot of difference. It would be interesting to hear from users
    who have gone this route. ?

    Regards

    Mike
     
    Mike, Dec 12, 2004
    #6
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