Upgrading memory in GA 8KNXP rev2. Which sockets?

Discussion in 'Gigabyte' started by Brian Griffin, Apr 2, 2009.

  1. At the moment I have two 512MB modules in slots 1 and 4. I want to upgrade
    to a total of 3GB by using two additional 1GB modules to make a total of
    four modules. The Users manual says "If four DDR memory modules are
    installed, (two pairs of DDR memory modules with the same memory size and
    type): The Dual Channel Technology will operate when a pair of DDR memory
    modules are inserted into DIMM 1, 4 and another pair into DIMM 2, 5." Do the
    two pairs have to be the same or can one pair be 512MB (in slots 1, 4) and
    the other pair be 1GB (in slots 2,4) or do all four modules have to be
    identical?
    Cheers,
    Brian
     
    Brian Griffin, Apr 2, 2009
    #1
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  2. Brian Griffin

    Paul Guest

    For dual channel, you want the same memory dimensions for the modules
    that are paired. The pairs can be different than one another, so your
    2x512MB + 2x1GB configuration should be OK, using them as you describe.

    875 memory guide
    (See Figure 5 & Figure 6 on Page 11)
    ftp://download.intel.com/design/chipsets/applnots/25273001.pdf

    The configuration you'll be using, is called "Normal Mode" in the
    guide. I wouldn't expect a big difference in performance between
    Normal Mode and Dynamic Mode. (Page 13 has a table, which ranks
    the different modes, but the table lacks numbers to show how
    significant the effects are.)

    To test, you can try a benchmark with just the pair of 1GB
    installed, and then rerun the benchmark with all four installed.
    On my 875 machine, using memtest86+ bandwidth indicator, I
    didn't get any difference in measured bandwidth, but that
    isn't really unexpected, due to the sequential access pattern.
    It is really hard to say, exactly what program would gain
    a big advantage from any of these modes that rely on
    interleave patterns or "open" pages.

    For a benchmark, I recommend SuperPI as a simple, single threaded
    test. You pick a number of digits, which results in the memory
    footprint not fitting entirely in cache. Since a P4 has a
    relatively small cache, you can use 1 million digits of PI
    calculation as your test. 1 million digits seems to use
    8MB of RAM (the P4 cache is smaller than that). Larger numbers
    of digits take longer to calculate, and for some of the processors
    with larger cache, or faster execution times, people use the
    32 million digit test.

    This bench was written a long time ago. The source is no longer
    available (a guy in Japan wrote it). Improvements to the program
    have been made over the years, by adding extra bytes with a hex
    editor. So if the program seems a little antique looking, there
    is a reason for that.

    http://www.xtremesystems.com/pi (I cannot reach here right now)

    http://www.techpowerup.com/downloads/366/

    On my P4 and AthlonXP 3200+ systems, this benchmark takes 45-50
    seconds to complete, for 1 million digits. The 50 second number
    was on the machine that was running AV in the background. The
    P4 was running at 3.1GHz. So that is the ballpark range I'd
    expect to see.

    You may be wondering, why the Intel document only refers to
    four slots, when your board has six. Your board is an anomaly,
    in the sense that Gigabyte has chosen to fool you into thinking
    it can use a lot of RAM. They used a trick which was used back
    in the single channel days. They add an extra slot to a channel,
    then cross-wire the ranks. The chipset can control four ranks
    (sides) of memory per channel (which I show below as A,B,C,D).
    The three DIMMs per channel on your board, is a total of six sides.
    This is the wiring pattern. Six physical sides, but only four
    controls for them.

    Slot 1 A
    B

    Slot 2 C
    D

    Slot 3 D
    C

    If you wanted to put RAM in both slot 2 and slot 3, the RAM could
    only be single sided. (Thus C gets used in slot 2, and D gets used
    in slot 3.) If you put a double sided stick in slot 2, that
    uses both C and D, and then nothing can go into slot 3.

    HTH,
    Paul
     
    Paul, Apr 2, 2009
    #2
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  3. Sorry but I've just noticed a slight error in my question. the last line
    should have read ". . . the other pair be 1GB (in slots 2, 5) [not 2, 4] or
    do . . .". Apologies to all.
     
    Brian Griffin, Apr 2, 2009
    #3
  4. Thanks, I can see what you say about running in normal mode but hopefully it
    won@t be a problem. The memory is on order.
    Cheers,
    Brian
     
    Brian Griffin, Apr 2, 2009
    #4
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