Mixing RAM

Discussion in 'Asus' started by Jab, Aug 31, 2005.

  1. Jab

    Jab Guest

    Perhaps this is daft but I'd thought I would enquire anyway.

    With the ASUS K8V-X board, which set-up is best to use:
    [ NB: I have the 2x256MB PC3200 already ]

    a) 1x1GB Pc3200 + 2x256MB Pc3200
    b) 2x512MB Pc3200
    c) 1x1GB Pc3200

    Is there a problem with a) ?

    Any help is appreciated!

    Jonny
     
    Jab, Aug 31, 2005
    #1
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  2. Jab

    Paul Guest

    In article <>, "Jab"
    <> wrote:

    > Perhaps this is daft but I'd thought I would enquire anyway.
    >
    > With the ASUS K8V-X board, which set-up is best to use:
    > [ NB: I have the 2x256MB PC3200 already ]
    >
    > a) 1x1GB Pc3200 + 2x256MB Pc3200
    > b) 2x512MB Pc3200
    > c) 1x1GB Pc3200
    >
    > Is there a problem with a) ?
    >
    > Any help is appreciated!
    >
    > Jonny


    It depends on your definition of "best".

    Most people would want a good combination of speed
    and size for the memory. Download the PDF user manual
    for the K8V-X and have a look at Table 1. It has various
    combinations of single and double sided sticks. It would
    seem the table for this board is not the standard one
    issued by AMD (as AMD made the original version of this
    table). The K8V-X table is more conservative than the average
    "Table 1", as normally you can run two double sided DIMMs
    at DDR400. (For example, download the manual for the
    K8N-E Deluxe, and look at the Table 1 in there.)

    The characteristics of the processor determine what
    Table 1 looks like, not the motherboard. That is because
    the memory controller is inside the processor. In the case
    of an S754 processor, there are two address busses and
    one data bus. The single data bus is what makes the processor
    a "single channel" processor. One address bus is connected
    to slot 1, and the other address bus is connected to slot
    2 and slot 3. That is why Table 1 is so weird looking,
    as the best configurations will be when the address bus
    loading is "shared" between the two address busses.

    Now, at the processor level, there are various steppings.
    If I go to www.amdcompare.com, and look at the processors
    available for S754, I see that the Athlon64 processors are
    still 130nm. Some of them are old enough, that they might
    not even have a Command Rate setting in the BIOS, which
    means the only user option is to drop the memory bus clock
    rate. A Sempron in the list looked like it was based on
    Rev.E, and potentially, that processor would have better
    memory drive characteristics. It means selecting a processor
    with the best processing characteristics, and best bus
    driving characteristics, is a bit harder. (Sempron P.R.
    ratings are slower than their Athlon64 counterparts.)

    Look for section 1.4 "Register Differences in Revisions of
    the AMD Athlon 64 and AMD Opteron Processors" in this
    document. It mentions that Command Rate "Enable 2T" was
    added to processor revision CG (or later steppings).

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

    This document has a nice geneology table. Table 1. "CPUID
    Values for Revisions of the Processors", using the third
    column over, shows S754 processors are available in C0,
    CG, and D0 steppings, and C0 is too old to support the
    "Enable 2T" setting.

    http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/25759.PDF

    If you go to www.amdcompare.com and list the S754 processors,
    there are rev.E Semprons listed (90 nm internal geometry),
    but Semprons are lesser processors when compared to the
    Athlon64 ones (the Sempron P.R. rating is comparable to an
    Intel Celeron's clock speed equivalent). Amdcompare lists
    some C0 stepping S754 processors, and I really have trouble
    believing they would still be shipping those - in any case,
    you want a CG or D0 stepping. Now, doc 25759 says there are
    D0 S754 processors, but amdcompare doesn't show _any_ in their
    list. Maybe all these sources of info are not up to date.

    Returning to the memory config options that you listed:

    I would pick (c) as the least risky configuration. It won't
    matter what kind of processor drives it. DDR400 should not
    be a problem.

    Your option (b) is a bit tougher for the processor to drive.
    Depending on which version of the Asus Table 1 you choose to
    believe, it will run at either DDR400 or DDR333. If you have
    a processor with an "Enable 2T" Command Rate setting, that
    gives you another "knob" to twist, if the RAM is not stable.
    Enabling 2T reduces RAM performance, but gives the address
    more time to settle on the address busses.

    Your option (a) is the heaviest loading case. Be prepared
    to drop the memory clock to either DDR333 or DDR266,
    depending on whether all three sticks are double sided or
    not. For example, if you are doing Photoshop, and need
    all the memory you could get, it would be better to use
    3x1GB DIMMs and take the hit on memory bus speed, than
    to use less memory, which would cause Photoshop to hit the
    scratch disk more. For most day to day activities, a lot
    of RAM is not going to be that useful, so the drop in
    memory speed may be a poorer compromise.

    Also, keep the memory performance thing in perspective,
    as the Athlon64 has very good cache characteristics, and
    doesn't suffer too much from a non-optimal memory config.

    So, that is the view from the theoretical side of things.
    Now, you'll need to visit the private forums, and see
    what memory speeds real users have managed to squeeze from
    their processors :)

    Paul
     
    Paul, Aug 31, 2005
    #2
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  3. Jab

    DaveW Guest

    The 2 x 512MB PC3200 sticks installed in the dual channel RAM configuration
    will probably give you the fastest memory configuration.

    --
    DaveW
    "Jab" <> wrote in message
    news:...
    > Perhaps this is daft but I'd thought I would enquire anyway.
    >
    > With the ASUS K8V-X board, which set-up is best to use:
    > [ NB: I have the 2x256MB PC3200 already ]
    >
    > a) 1x1GB Pc3200 + 2x256MB Pc3200
    > b) 2x512MB Pc3200
    > c) 1x1GB Pc3200
    >
    > Is there a problem with a) ?
    >
    > Any help is appreciated!
    >
    > Jonny
    >
     
    DaveW, Aug 31, 2005
    #3
  4. Jab

    Jab Guest

    Thanks for the detailed reply Paul, I'm a lot clearer on the inner
    workings now.

    With your advice, I went for a 1Gb PC3200 stick, with the view to
    upgrading to 2Gb later. I'm lead to believe from the manuals and what
    you have said about the processor having the memory characteristics
    build-in; that a single chip will perform the same as dual channel.

    I might stick in the 2x256 (they are single sided) and see what happens
    with speed versus size issue, but I don't expect to exceed the 1Gb too
    often! But I'll keep an eye on that.

    I will run a benchmarking program for both set-ups and see if there's
    much of a difference.

    Also, the chip I've went for is the AMD clawhammer, complete with 1Mb
    of cache, so perhaps memory config will be less of an issue.

    Thanks again for the great advice,

    Jonny
     
    Jab, Sep 1, 2005
    #4
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