Memory speed rating ..... Is it "the higher the better" or ...?

Discussion in 'Asus' started by Mark, Sep 20, 2004.

  1. Mark

    Mark Guest

    Dear All, re- the Memory speed rating ..... Is it " the
    higher the better " ?
    I am using the Asus P4S533E Mobo and would like
    to ask if I should fit it with an
    Apacer 512MB DDR RAM 400Mhz PC3200 or a
    333Mhz PC2700 memory module for better (faster)
    The price difference between the two Apacer cards
    appears to be minimal.
    Mark, Sep 20, 2004
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  2. Mark

    Paul Guest

    The relationship isn't quite as simple as that, but your rule
    is good enough in this case. Sometimes, a cycle or two of
    access delay can be removed, when the CPU clock and the memory
    clock are the same. When they are run at different frequencies
    (asynchronous), then the logic adds resync delays. That drops
    the performance, and to get the performance back, the clock speed
    has to be raise a bit more to compensate. So, the relation isn't
    a simple one. Even the performance curve is not smooth - there
    are "bumps" in the curve, caused by the quantization of clock
    ticks. But, glossing over the details, more is better.

    Your board has official support for DDR333 and some people
    run faster than that. If running at DDR400, you might only
    expect one double sided DIMM to work at that speed. Place it
    in the slot furthest from the processor. Use Google to find what
    ratios are available, as that isn't documented in detail in the
    manual. The CPU clock, the CPU:Mem ratio, determine the speed
    of the memory. Not all available options work well, so before
    booting Windows with a new set of conditions, use memtest86
    from to test the memory. Do not boot into
    Windows until memtest can do some passes without error.
    Memtest86 is a floppy based test program, and it doesn't need
    an OS to work (it is self booting).

    At DDR400 rates, sometimes the RAM needs a little extra voltage
    to work well. PC2700 or lower ram is usually rated for 2.5V.
    PC3200 and higher needs a minimum of 2.6V to work well at DDR400.
    Overclocker memory sometimes needs a bit more (like the Mushkin
    BH-6, which needs closer to 2.8V to perform well). As at least
    some memory chips have internal voltage regulation for parts
    of the memory, raising the voltage a lot, results in the memory
    running hotter, and hotter memory runs slower. So, like everything,
    there are limits to the benefits that higher voltage can bring.
    Earlier motherboards don't have controls for setting Vdimm, so
    that can be another reason for a memory not to perform well.
    In this case, the upper limit is likely to be the Northbridge.

    Paul, Sep 20, 2004
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  3. Mark

    Mark Guest

    Sum it up for me Paul ..... In my case, should I purchase the
    PC2700 card or the PC3200 one for best 'bang for the buck'
    (and keeping in view possible future Mobo upgrades) if I
    don't intend to overclock.
    There won't be any problems running the 400Mhz module at
    333Mhz ... will there?
    thanks Paul
    Mark, Sep 21, 2004
  4. Mark

    Paul Guest

    Buy the PC3200. RAM is backward compatible, and the PC3200
    can run at DDR400, DDR333 etc.

    In terms of experiences, there are enough entries in Google,
    to get a good feeling for what level of overclock you can
    expect to get working. I'd try to help you further, but
    I don't know what CPU:Mem ratios are offered in the BIOS
    for each FSB speed.

    Paul, Sep 21, 2004
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