dual channel ram configuration for dual processors on Asus K8N-DL

Discussion in 'Asus' started by wang chung, Apr 26, 2006.

  1. wang chung

    wang chung Guest

    Im making a system using the K8N-DL and 2x Opteron 265s. I want to get
    the full potential out of the board with bus speeds and utilizing dual
    channel ram. The mobo manual states for dual cpu you need this ram bank
    configuration: DIMM_A1+DIMM_A2=DIMM_B1+DIMM_B2=DIMM_A3+DIMM_B3. Does
    this mean you need 6 sticks of ram? or 3 or what? I was planning on 6x
    512 sticks but I read something that said using 6 sticks will degrade
    ram performance. I just want to buy the right stuff. Can someone
    advise me please? Thanks
     
    wang chung, Apr 26, 2006
    #1
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  2. wang chung

    Paul Guest

    Wow, that description in the manual is just terrible!

    If it was my board, I would put two sticks of RAM on each
    processor. I would buy four identical sticks. They could be
    512MB each (for a 2GB system total) or 1GB each (for a 4GB system
    total). I don't know if there are issues with going larger than
    that or not, as the processor contains the memory controller,
    and I haven't read any accounts of using a 2GB or 4GB sized
    registered DIMM. (The AMD 26094 document contains more info,
    but is not a user friendly document.) Using two sticks per
    processor, is the highest speed configuration for the
    memory clock. Using four double sided sticks on one processor,
    usually means a (small) speed penalty.

    http://forums.2cpu.com/showthread.php?t=63239&page=31&pp=30&highlight=k8n-dl

    The way the original Athlon64 was described, is not really
    dual channel in the most flexible sense. AMD started with
    the concept of either 64 bit wide memory, or 128 bit wide
    memory. When you install a DIMM on one channel, the corresponding
    DIMM slot on the other channel has to be populated, for the
    two DIMMs to be fed identical address/control info, and for
    the two of them to function as a "128 bit wide" uber-DIMM.
    That is what dual channel means to AMD.

    Based on that premise of operation, A1=B1, A2=B2, A3=B3 would
    be the best rule to follow to allow 128 bit wide operation.
    If you populate A1, then you should also populate B1. And so
    on.

    To use four sticks, then A1=B1 and A3=B3, would be one
    solution. Or A2=B2 and A3=B3 is the second solution.

    By means of the interconnected Hypertransport busses, it is
    possible for one processor to access the memory of the
    other processor. In fact, there are some dual socket AMD
    motherboards, where the second processor has no memory slots,
    and thus the second processor "leeches" off the memory belonging
    to the first processor.

    940 pin memory population rules are on Pg. 184 (table 49). I
    notice quad rank (whatever that is, 36 chips per module?) are
    mentioned, with an appropriate speed penalty for their use. If
    you stick with two double-sided registered DIMMs per processor,
    you can stay at DDR400.

    http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26094.PDF

    You might dig up more info on forums.2cpu.com. Search engine:

    http://forums.2cpu.com/search.php

    And finally, this article discusses various interleaving options
    on multiprocessor Opteron boards.

    http://www.digit-life.com/articles2/cpu/rmma-numa.html

    Hope that gets you started,
    Paul
     
    Paul, Apr 26, 2006
    #2
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  3. wang chung

    Robert Guest


    I built one, the RAM instructions in manual are slightly incorrect. The
    pairing is wrong. If u follow the pairing plan u end up with non-dual
    channel. You need to match the colours for each 2 sticks of RAM.

    The first 4 slots are for CPU 1. The last 2 slots are for the CPU 2.

    Remember that there may be a limitation for the amount of RAM that the OS
    can use. For example if its a server and you're using Windows Small
    Business Server 2003 then its 4GB limitation.

    The manual is probably the worst manual I've ever seen for a RAID enabled
    motherboard. It doesn't even have a section about the RAID setup, not even
    1 page or 1 paragraph.
     
    Robert, May 17, 2006
    #3
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