fsb:dram & p5l-mx

Discussion in 'Asus' started by Trin, Dec 13, 2007.

  1. Trin

    Trin Guest


    I have a p5l-mx mobo and i've been researching something
    for half a day.

    I'm using core 2 duo 4300 at 800 FSB. My memory is
    DDR2-667 with a fsb:dram ratio of 3:5. It is said that
    1:1 fsb:dram ratio is optimum. Does this mean using a
    DDR400 giving a ratio of 1:1 would produce faster output
    than the DDR2-667? If not, why not?


    Trin, Dec 13, 2007
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  2. Trin

    Paul Guest

    The faster it goes, the better. I think it is possible
    the FSB is FSB1066 here, so DDR2-533 is a good starting
    point, but the faster RAM options do help.


    It is all a question, of whether the percentage increase
    in application performance, justifies spending more for
    the memory.

    Paul, Dec 13, 2007
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  3. Trin

    Trin Guest

    The P5l-MX has maximum of FSB 800 & DDR2-667. I remember
    reading a year back or so that DDR2-667 is slower than DDR2-533
    or DDR2-400 and I can't find the articles anymore. What
    configuration can this slowing down occur?

    Trin, Dec 13, 2007
  4. Trin

    Paul Guest

    In previous generations of computers, there was a difference
    between "synchronous" operation, and async operation. When running
    async, resynchronization would add latency (delay) to the path between
    memory and processor. The result was, that to get an advantage
    from running async, you had to crank the memory quite high,
    to compensate for the extra latency.

    To give an example, if you had a FSB266 processor, and tried to
    run memory at DDR333, it might be slower than if run at DDR266.
    That is because the DDR333 needed resynchronization. If the
    memory speed was further increased to DDR400, then that config
    of FSB266/DDR400, would be faster than FSB266/DDR266.

    That no longer seems to be the case. Now you can run async, and
    have memory faster than FSB, and get some additional benefit.

    Paul, Dec 13, 2007
  5. Trin

    Trin Guest

    How come in the above example the DDR400 doesn't need
    resynchronization making the FSB266/DDR400 combo as you
    mentioned faster?
    How do you tell which mobo has the invariant syncs
    specs that doesn't produce slowdown compared to
    those that produce slowdowns? Any particular bios
    signature or something? Or northbridge feature? I
    heard core 2 duos needs synchronization for faster
    results? It is no longer required too in newer mobos?

    Trin, Dec 13, 2007
  6. Trin

    DaveW Guest

    Wrong. You are confusing DDR RAM and the newer and faster DDR2 RAM. You
    need to use ONLY DDR2 RAM in that motherboard. It is incompatible with the
    older DDR RAM.
    DaveW, Dec 13, 2007
  7. Trin

    Trin Guest

    I know since the PL5-MX only allows DDR2-400, DDR2-533 and
    DDR2-667. But since the fsb of the mainboard is 200 x 4 = 800.
    The memory should supposedly be DDR2-400 so the fsb:dram
    can be 1:1 due to the similar 200 initial clock. What I'd like
    to know is how does one tell which mainboard doesn't cause
    slowdown from resynchronization? What particular technical
    spec to look for and how does those newer boards able to make
    it in such a way that no resynchronization is required in say
    using a DDR2-667 to produce an fsb:dram of 3:5 from the memory
    333 clock versus the 200 clock of the cpu?

    Trin, Dec 13, 2007
  8. Trin

    Paul Guest

    That is because there are two factors at work. The latency introduced
    by resynchronization is one effect. It is a negative. But when the
    memory gets faster, that is a positive. At DDR400, the positive factor
    has a greater effect, than the negative one, and the configuration is
    better as a result.
    I haven't seen any performance results for DDR2, that differ
    from the one I showed. So I still think you will be ahead by
    using a faster RAM. But the improvement is percentage points,
    so you can look at the cost, and the amount of improvement,
    and decide whether it is worthwhile or not.

    Running in dual channel, with a couple matched sticks, is
    going to help you as much as some difference in the clock
    rate. So at least use a dual channel setup.

    Paul, Dec 14, 2007
  9. Trin

    Paul Guest

    Also, it occurs to me, that you can buy DDR2-667 memory, and
    experiment with it. You can change the memory bus clock and test
    performance by using an application. Use something like SuperPI
    for example, and see which speed setting is best. Buying the
    faster RAM, will allow you to run at all three supported speeds.
    Faster RAM can run at a slower speed, if desired.


    Paul, Dec 14, 2007
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