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Memory v.s. Processor speed (Athlon 64x2)

Discussion in 'AMD Overclocking' started by Joe101, Jul 4, 2007.

  1. Joe101

    Joe101 Guest

    Can someone explain 64x2 processor and memory speed combinations. Is it
    correct to assume any 64x2 processor speed will work with any memory speed
    except at possibly reduced efficiency? What are the max processor speeds
    what till run with each of the following DDR-800, DDR-667, and DDR -533?
     
    Joe101, Jul 4, 2007
    #1
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  2. "Joe101" <> wrote in message
    news:tVUii.8445$...
    > Can someone explain 64x2 processor and memory speed combinations. Is it
    > correct to assume any 64x2 processor speed will work with any memory speed
    > except at possibly reduced efficiency? What are the max processor speeds
    > what till run with each of the following DDR-800, DDR-667, and DDR -533?
    >
    >

    On a good AM2 motherboard, CPU frequency and memory frequency are separate
    issues, and can be controlled individually. Having slower memory will slow
    your system a bit, but you can use any X2 CPU with any of the DDR2 speeds
    you've listed. My Asus M2N-E allows me to set CPU frequency to anything
    between 200 (stock) up to 400, and separately, I set memory clock frequency
    to anything between DDR2-400 to DDR2-800.
    You would need to check out the BIOS features of the motherboard you want to
    see if it allows the same degree of control.

    Oh, one other thing. DDR2 memory is cheap right now, so I'd advise getting
    good quality DDR2-800 to get best overall performance.
     
    Peter van der Goes, Jul 5, 2007
    #2
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  3. Joe101

    Ed Light Guest

    Don't forget that when you increase the clock speed up from 200, the
    memory speed increases proportionately, so if your memory won't
    overclock you'd set it to a lower speed and calculate how high the clock
    could go before you'd have to set it to a still lower speed because it
    had come back up to its stock speed.

    For instance, on my old nforce 3 with DDR 400, I overclocked it from
    clock 200 to 240, 20%. So, when I set the memory to 333 (same as 166),
    it came back up to 400.

    However, there's the timing issue. The motherboard sees that the memory
    is set to a slower speed, so it decides to tighten up the timings. Then
    when the memory actually comes back up to a normal speed, the timings
    may be too tight and cause errors. To avoid that I start out stock with
    the memory the way it's meant to be and lock the timings by going to
    manual timings. Then they shouldn't change any more, but I write down
    the numbers and check them later.

    ---
    Ed Light

    Bring the Troops Home:
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    Send spam to the FTC at

    Thanks, robots.
     
    Ed Light, Jul 5, 2007
    #3
  4. "Ed Light" <> wrote in message
    news:eek:O%ii.224271$...
    > Don't forget that when you increase the clock speed up from 200, the
    > memory speed increases proportionately, so if your memory won't overclock
    > you'd set it to a lower speed and calculate how high the clock could go
    > before you'd have to set it to a still lower speed because it had come
    > back up to its stock speed.
    >
    > For instance, on my old nforce 3 with DDR 400, I overclocked it from clock
    > 200 to 240, 20%. So, when I set the memory to 333 (same as 166), it came
    > back up to 400.
    >
    > However, there's the timing issue. The motherboard sees that the memory is
    > set to a slower speed, so it decides to tighten up the timings. Then when
    > the memory actually comes back up to a normal speed, the timings may be
    > too tight and cause errors. To avoid that I start out stock with the
    > memory the way it's meant to be and lock the timings by going to manual
    > timings. Then they shouldn't change any more, but I write down the numbers
    > and check them later.
    >
    > ---
    > Ed Light
    >
    > Bring the Troops Home:
    > http://bringthemhomenow.org
    > http://antiwar.com
    >
    > Send spam to the FTC at
    >
    > Thanks, robots.


    Hi, Ed.
    While what you say about the memory speed increasing with clock speed is
    true with some chipsets (I believe my NFORCE 4 board acts as you describe,
    and I know my Asus P5B-Plus does). I don't think it's true of my Asus M2N-E
    (NFORCE 580 chipset). With the 580, I get the behavior you describe if I set
    memory speed to Auto, but if I select a specific memory speed, that
    decouples the memory speed from the clock speed and allows me to set my
    clock at 240 and not affect memory speed. When I run tests on the M2N-E PC,
    using SiSoft Sandra, it shows the memory at the manually set speed despite
    the clock speed increase. On my P5B-Plus, Sandra shows an increased memory
    speed proportional to clock speed increases as the chipset on that board
    will not decouple the memory clock.
     
    Peter van der Goes, Jul 5, 2007
    #4
  5. Joe101

    Ed Light Guest

    Ed Light, Jul 5, 2007
    #5
  6. Joe101

    Guest

    I think ram speeds are address by the Front side bus speed.
    something about diveded by four to get your ram speed?? Any gurus in
    this area?
    I want to get a AMD k2 6000, and am having trouble trying to find the
    correct information for the recomended ram speed.
     
    , Jul 22, 2007
    #6
  7. Joe101

    Paul Guest

    wrote:
    > I think ram speeds are address by the Front side bus speed.
    > something about diveded by four to get your ram speed?? Any gurus in
    > this area?
    > I want to get a AMD k2 6000, and am having trouble trying to find the
    > correct information for the recomended ram speed.
    >


    No.

    http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2741&p=3

    The processor has the memory controller on it. By means of
    clock synthesis logic on the processor, it can generate clocks
    suitable for running memory at or close to DDR2-400, DDR2-533,
    DDR2-667, DDR2-800. In other words, you can use any memory you
    want. Since DDR2-800 memory is available, you could buy a couple
    sticks of that.

    People calculate these tables, to demonstrate what the synthesis
    logic can do. The idea is, the synthesized clock for the memory,
    is at or below the value specified by the user in the BIOS screen.
    If you set DDR2-800 in the BIOS screen (with core at nominal speed),
    this table is not allowed to set the memory on purpose so it runs
    at DDR2-801 or higher. But it can use DDR2-799 if the hardware can
    make that value. Overclocking doesn't count in the logic, and
    the processor doesn't "know" it is being overclocked - it is
    oblivious.

    http://forums.hardwarelogic.com/f11/memory-divider-table-1408.html

    The memory can be used in a couple of ways.

    If you set the processor input clock to 200MHz, that is "stock".
    If you set the memory interface to "DDR2-800", that is what you get.

    Now, let's try a second case. Set the memory controller to DDR2-667,
    even though the memory is rated at DDR2-800. Now, increase the processor
    input clock to 200 * (800/667) or about 240MHz. That causes the processor
    core to be overclocked by 20%. So it runs 20% faster than normal. Now,
    what happens to the memory. Well, the memory clock also depends on the
    processor input clock. If the processor input clock increases, so
    does the memory clock. If the memory was set to 667, and is now going
    20% faster than that, that is 667 * 1.20 = 800, and so the memory is
    exactly in spec. (I.e. The BIOS says "DDR2-667", but the hardware is really
    running at DDR2-800 due to the CPU clock choice.)

    In other words, you can turn down the memory setting, turn up the
    CPU input clock, overclock the core, and yet the memory is still in
    spec.

    Naturally, all hardware has some interface limits, so buying DDR2-1066
    memory might not make sense for an AMD processor. The speed of the
    memory you buy, is really a measure of the utility you get from it.
    If fast memory only bought you 5% more performance, then spending
    an extra $200 to get that performance would be stupid. You'd be
    better off buying a more capable processor (whatever that is), and
    cheaper memory.

    So use a little common sense, and buy what everyone else buys :)
    AM2 is positioned currently, for low to mid range systems, so
    laying out hundreds of dollars for special memory makes no sense
    at all.

    If you take a quick look through the reviews here, I see mention
    of people using DDR2-800, and that is what I'd buy.

    http://www.newegg.com/Product/ProductReview.aspx?Item=N82E16813131013

    Paul
     
    Paul, Jul 22, 2007
    #7
  8. Joe101

    Wes Newell Guest

    On Sun, 22 Jul 2007 04:22:25 -0700, vyaw2003 wrote:

    > I think ram speeds are address by the Front side bus speed.
    > something about diveded by four to get your ram speed?? Any gurus in
    > this area?
    > I want to get a AMD k2 6000, and am having trouble trying to find the
    > correct information for the recomended ram speed.


    In addition to Pauls very excellent reply, remember that memory speed
    usually has very little affect on overall system performance since 90% of
    all memory accesses are usually serviced by the CPU cache, never even
    really bringing the memory speed into play. As a rule I always buy the
    fastest with a reasonable price. Right now ddr2-533 and ddr2-667 is about
    the same price, with ddr2-800 only being slightly higher. Anything above
    that is considerably higher. Ref. Pricewatch. So today I'd get ddr2-667 or
    ddr2-800. Of course it's all dirt cheap these days compared to 20 years
    ago.:)

    --
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    Wes Newell, Jul 22, 2007
    #8
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