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C2D Overclocking Techniques Asus P5B-Plus

Discussion in 'Overclocking' started by Peter van der Goes, Jun 28, 2007.

  1. I read in another thread in this group that you should:

    "Unlink the memory clock from the CPU clock and run the memory at its stock
    specifications" (thanks to Phil Weldon)

    In my P5B-Plus BIOS (after setting the AI Overclock to manual) I have a
    setting for CPU frequency, adjustable in 1 MHz increments. This setting is
    linked to DRAM frequency as any change in CPU frequency reflects as an
    equivalent change in DRAM frequency.

    To keep my memory in spec, I originally set my DRAM frequency to DDR2-533MHz
    because I knew it would increase with increases in CPU frequency.
    Presently, I've raised the CPU frequency from the original 267 to 333, which
    has put my DRAM frequency at DDR2-667MHz.
    That's a modest overclock for my 6420, now running at 2.67GHz.

    Now that I've acquired a 3rd party HSF (the Intel HSF is barely able to cope
    with the current settings), I'd like to raise the CPU frequency in small
    increments, but I really prefer to leave my DRAM frequency where it is.

    The only settings available for DRAM frequency are DDR2-533, DDR2-667,
    DDR2-800, DDR2-889, DDR2-1067 and AUTO.
    Unfortunately the manual does not describe the effects of using AUTO, but
    that would appear to be the only possible way to unlink the memory clock
    from the CPU clock, if AUTO somehow means set by interrogating the memory
    modules themselves (used to be called "by SPD" IIRC).

    Am I on the right track to decoupling CPU clock and DRAM frequency, or is
    there some other BIOS setting I've missed completely?

    TIA for any enlightenment/suggestions.
    Peter van der Goes, Jun 28, 2007
    #1
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  2. Peter van der Goes

    Phil Weldon Guest

    'Peter van der Goes' wrote, in part:
    |I read in another thread in this group that you should:
    |
    | "Unlink the memory clock from the CPU clock and run the memory at its
    stock
    | specifications" (thanks to Phil Weldon)
    |
    | In my P5B-Plus BIOS (after setting the AI Overclock to manual) I have a
    | setting for CPU frequency, adjustable in 1 MHz increments. This setting is
    | linked to DRAM frequency as any change in CPU frequency reflects as an
    | equivalent change in DRAM frequency.
    |
    | To keep my memory in spec, I originally set my DRAM frequency to
    DDR2-533MHz
    | because I knew it would increase with increases in CPU frequency.
    | Presently, I've raised the CPU frequency from the original 267 to 333,
    which
    | has put my DRAM frequency at DDR2-667MHz.
    | That's a modest overclock for my 6420, now running at 2.67GHz.
    _____

    Overclocking is a voyage of discovery. Different motherboard manufacturers
    customize BIOS settings in different ways. Some chip sets allow setting
    parameters that are not available when other chip sets are used. Generally
    the motherboard manuals provided don't offer much explanation, and seem to
    be the product of several translations back and forth among several
    languages - and even different concepts of math B^)

    Form a cursory look at the manual for your P5B Plus motherboard, it seems to
    me that selecting a memory speed from the list under 'DRAM Frequency' in the
    'Advanced Chipset Settings' page

    [Auto]
    [DDR2 - 533MHz]
    [DDR2 - 667MHz]
    [DDR2 - 800MHz]
    [DDR2 - 889MHz]
    [DDR2- 1067MHz]

    sets the memory speed to specific frequencies that are not linked to the CPU
    speed, with the [Auto Selection] possibly a setting to link the Memory Clock
    to a multiple of the CPU Clock, probably 1:2].

    I'd guess that you are wrong in assuming that increasing the CPU clock speed
    increases the Memory clock speed UNLESS the 'DRAM Frequency' setting is
    [AUTO]. The English version of the manual is ambiguous on this and other
    points. There does not seem to be the flexibility in the BIOS settings
    that, for example, the nVidia 680i chipset has for memory frequency where
    any memory bus frequency can be set independently from the FSB frequency
    (though there is some granularity.)

    For your particular concern, I'd set the 'DRAM Frequency' to the
    specification of your memory modules, and assume that the memory clock
    frequency would be fixed. If you, after getting a stable CPU overclock,
    wish to overclock your memory, it seems that only certain fixed memory speed
    steps are avaliable in the BIOS. Perhaps the ASUS OS based overclocking
    application has additional flexibility.

    Try it and check the results.

    Phil Weldon


    "Peter van der Goes" <> wrote in message
    news:VGCgi.235360$...
    |I read in another thread in this group that you should:
    |
    | "Unlink the memory clock from the CPU clock and run the memory at its
    stock
    | specifications" (thanks to Phil Weldon)
    |
    | In my P5B-Plus BIOS (after setting the AI Overclock to manual) I have a
    | setting for CPU frequency, adjustable in 1 MHz increments. This setting is
    | linked to DRAM frequency as any change in CPU frequency reflects as an
    | equivalent change in DRAM frequency.
    |
    | To keep my memory in spec, I originally set my DRAM frequency to
    DDR2-533MHz
    | because I knew it would increase with increases in CPU frequency.
    | Presently, I've raised the CPU frequency from the original 267 to 333,
    which
    | has put my DRAM frequency at DDR2-667MHz.
    | That's a modest overclock for my 6420, now running at 2.67GHz.
    |
    | Now that I've acquired a 3rd party HSF (the Intel HSF is barely able to
    cope
    | with the current settings), I'd like to raise the CPU frequency in small
    | increments, but I really prefer to leave my DRAM frequency where it is.
    |
    | The only settings available for DRAM frequency are DDR2-533, DDR2-667,
    | DDR2-800, DDR2-889, DDR2-1067 and AUTO.
    | Unfortunately the manual does not describe the effects of using AUTO, but
    | that would appear to be the only possible way to unlink the memory clock
    | from the CPU clock, if AUTO somehow means set by interrogating the memory
    | modules themselves (used to be called "by SPD" IIRC).
    |
    | Am I on the right track to decoupling CPU clock and DRAM frequency, or is
    | there some other BIOS setting I've missed completely?
    |
    | TIA for any enlightenment/suggestions.
    |
    |
    Phil Weldon, Jun 28, 2007
    #2
    1. Advertising

  3. "Phil Weldon" <> wrote in message
    news:swDgi.1675$...
    > 'Peter van der Goes' wrote, in part:
    >
    > Overclocking is a voyage of discovery. Different motherboard
    > manufacturers
    > customize BIOS settings in different ways. Some chip sets allow setting
    > parameters that are not available when other chip sets are used.
    > Generally
    > the motherboard manuals provided don't offer much explanation, and seem to
    > be the product of several translations back and forth among several
    > languages - and even different concepts of math B^)
    >
    > Form a cursory look at the manual for your P5B Plus motherboard, it seems
    > to
    > me that selecting a memory speed from the list under 'DRAM Frequency' in
    > the
    > 'Advanced Chipset Settings' page
    >
    > [Auto]
    > [DDR2 - 533MHz]
    > [DDR2 - 667MHz]
    > [DDR2 - 800MHz]
    > [DDR2 - 889MHz]
    > [DDR2- 1067MHz]
    >
    > sets the memory speed to specific frequencies that are not linked to the
    > CPU
    > speed, with the [Auto Selection] possibly a setting to link the Memory
    > Clock
    > to a multiple of the CPU Clock, probably 1:2].
    >
    > I'd guess that you are wrong in assuming that increasing the CPU clock
    > speed
    > increases the Memory clock speed UNLESS the 'DRAM Frequency' setting is
    > [AUTO]. The English version of the manual is ambiguous on this and other
    > points. There does not seem to be the flexibility in the BIOS settings
    > that, for example, the nVidia 680i chipset has for memory frequency where
    > any memory bus frequency can be set independently from the FSB frequency
    > (though there is some granularity.)
    >
    > For your particular concern, I'd set the 'DRAM Frequency' to the
    > specification of your memory modules, and assume that the memory clock
    > frequency would be fixed. If you, after getting a stable CPU overclock,
    > wish to overclock your memory, it seems that only certain fixed memory
    > speed
    > steps are avaliable in the BIOS. Perhaps the ASUS OS based overclocking
    > application has additional flexibility.
    >
    > Try it and check the results.
    >
    > Phil Weldon
    >

    I'll take a chance with it and let you know.
    The reason I'm a bit leery is that after selecting DDR2-533MHz for DRAM
    Frequency, making changes to the CPU Clock setting simultaneously changes
    the displayed speed in DRAM Frequency.
    Peter van der Goes, Jun 28, 2007
    #3
  4. I don't own a P5B. I am using a P5W DH instead.
    Here is how I understand what's happening for me:
    There is a link between the FSB frequency and the speed of the mem. The link
    comes from the fact that the CPU (or FSB) clock and the mem interface clock
    both derive from the same basic clock. So that there can only be fractional
    relations between them, like 1:1, 5:4, 4:3, etc. This is what is called the
    CPU/mem (or mem/CPU?) ratio.
    So what happens?
    When you choose one FSB frequency for the CPU, the advanced chipset settings
    will present you with DDR2-xxxMHz values which are indeed the FSB multiplied
    by the various fractions I mentionned. You can choose whichever value, at
    will, but provided you don't go too high and go over what the mem can do.
    Now, if you start by choosing DDR2-533MHz (which would correspond to a
    266MHz FSB and a 1:1 ratio) and subsequently change the FSB to 300MHz, then
    what you will find in chipset settings for the 1:1 ratio is DDR2-600MHZ. And
    other values which correspond to the 5:4, etc ratios of 300MHz. If 600MHz
    goes above the speed your mem can cope with, simply choose another value
    which, for example, would correspond to a 4:5 ratio (in this case,
    DDR2-480MHz).
    In other words, because it is the way the BIOS works (you choose an FSB
    frequency, and in fact a CPU/mem ratio although it is presented as a mem
    speed value), choose the FSB first and then adjust the chipset settings for
    the mem.
    That's how it works for my P5W DH, I guess it is the same for the P5B.
    Sorry I cannot be more precise on the DDR2-xxxMHz (or CPU/mem ratios)
    accessible, as I am not home where I use my P5W.
    I am not sure this is all clear?

    "Peter van der Goes" <> wrote in message
    news:0vGgi.652319$...
    >
    > "Phil Weldon" <> wrote in message
    > news:swDgi.1675$...
    > > 'Peter van der Goes' wrote, in part:
    > >
    > > Overclocking is a voyage of discovery. Different motherboard
    > > manufacturers
    > > customize BIOS settings in different ways. Some chip sets allow setting
    > > parameters that are not available when other chip sets are used.
    > > Generally
    > > the motherboard manuals provided don't offer much explanation, and seem

    to
    > > be the product of several translations back and forth among several
    > > languages - and even different concepts of math B^)
    > >
    > > Form a cursory look at the manual for your P5B Plus motherboard, it

    seems
    > > to
    > > me that selecting a memory speed from the list under 'DRAM Frequency' in
    > > the
    > > 'Advanced Chipset Settings' page
    > >
    > > [Auto]
    > > [DDR2 - 533MHz]
    > > [DDR2 - 667MHz]
    > > [DDR2 - 800MHz]
    > > [DDR2 - 889MHz]
    > > [DDR2- 1067MHz]
    > >
    > > sets the memory speed to specific frequencies that are not linked to the
    > > CPU
    > > speed, with the [Auto Selection] possibly a setting to link the Memory
    > > Clock
    > > to a multiple of the CPU Clock, probably 1:2].
    > >
    > > I'd guess that you are wrong in assuming that increasing the CPU clock
    > > speed
    > > increases the Memory clock speed UNLESS the 'DRAM Frequency' setting is
    > > [AUTO]. The English version of the manual is ambiguous on this and

    other
    > > points. There does not seem to be the flexibility in the BIOS settings
    > > that, for example, the nVidia 680i chipset has for memory frequency

    where
    > > any memory bus frequency can be set independently from the FSB frequency
    > > (though there is some granularity.)
    > >
    > > For your particular concern, I'd set the 'DRAM Frequency' to the
    > > specification of your memory modules, and assume that the memory clock
    > > frequency would be fixed. If you, after getting a stable CPU overclock,
    > > wish to overclock your memory, it seems that only certain fixed memory
    > > speed
    > > steps are avaliable in the BIOS. Perhaps the ASUS OS based overclocking
    > > application has additional flexibility.
    > >
    > > Try it and check the results.
    > >
    > > Phil Weldon
    > >

    > I'll take a chance with it and let you know.
    > The reason I'm a bit leery is that after selecting DDR2-533MHz for DRAM
    > Frequency, making changes to the CPU Clock setting simultaneously changes
    > the displayed speed in DRAM Frequency.
    >
    M. R. Carleer, Jun 28, 2007
    #4
  5. "M. R. Carleer" <> wrote in message
    news:f60a8i$rpl$...
    >I don't own a P5B. I am using a P5W DH instead.
    > Here is how I understand what's happening for me:
    > There is a link between the FSB frequency and the speed of the mem. The
    > link
    > comes from the fact that the CPU (or FSB) clock and the mem interface
    > clock
    > both derive from the same basic clock. So that there can only be
    > fractional
    > relations between them, like 1:1, 5:4, 4:3, etc. This is what is called
    > the
    > CPU/mem (or mem/CPU?) ratio.
    > So what happens?
    > When you choose one FSB frequency for the CPU, the advanced chipset
    > settings
    > will present you with DDR2-xxxMHz values which are indeed the FSB
    > multiplied
    > by the various fractions I mentionned. You can choose whichever value, at
    > will, but provided you don't go too high and go over what the mem can do.
    > Now, if you start by choosing DDR2-533MHz (which would correspond to a
    > 266MHz FSB and a 1:1 ratio) and subsequently change the FSB to 300MHz,
    > then
    > what you will find in chipset settings for the 1:1 ratio is DDR2-600MHZ.
    > And
    > other values which correspond to the 5:4, etc ratios of 300MHz. If 600MHz
    > goes above the speed your mem can cope with, simply choose another value
    > which, for example, would correspond to a 4:5 ratio (in this case,
    > DDR2-480MHz).
    > In other words, because it is the way the BIOS works (you choose an FSB
    > frequency, and in fact a CPU/mem ratio although it is presented as a mem
    > speed value), choose the FSB first and then adjust the chipset settings
    > for
    > the mem.
    > That's how it works for my P5W DH, I guess it is the same for the P5B.
    > Sorry I cannot be more precise on the DDR2-xxxMHz (or CPU/mem ratios)
    > accessible, as I am not home where I use my P5W.
    > I am not sure this is all clear?
    >

    Very clear, actually :)
    As Phil put it, "overclocking is a voyage of discovery". I've discovered
    that these motherboards with the Intel 965 chipset don't allow separation of
    CPU and memory speeds. So now I'll see if I can push the memory a bit more
    :)

    Thanks very much to both you and Phil for the information.
    Peter van der Goes, Jun 28, 2007
    #5
  6. I am not sure it comes from the chipset. It might come from a clock
    generator on the mobo. I don't know.
    Anyway, what is to be remembered is that in the BIOS you don't choose the
    CPU freq and the mem freq, but instead the CPU freq and a ratio between that
    and the mem freq. In the chipset settings, they present the mem freq which
    would derive from the chosen CPU freq and ratio, but what you effectively
    choose is the ratio without knowing. Of course, once you choose the ratio,
    changing the CPU freq also changes the mem freq as the ratio remains
    constant.
    Choosing Auto, the BIOS chooses the ratio for you so that the resulting mem
    freq is <= than the maximum defined by the mem module itself in the spd,
    choosing preferably the 1:1 ratio. Once again, that's what I found for the
    P5W. It might be different for the P5B.

    Oh, and you are welcome: it is the purpose of the newsgroups, to try to help
    one another.

    "Peter van der Goes" <> wrote in message
    news:EMOgi.1835$%...
    >
    > "M. R. Carleer" <> wrote in message
    > news:f60a8i$rpl$...
    > >I don't own a P5B. I am using a P5W DH instead.
    > > Here is how I understand what's happening for me:
    > > There is a link between the FSB frequency and the speed of the mem. The
    > > link
    > > comes from the fact that the CPU (or FSB) clock and the mem interface
    > > clock
    > > both derive from the same basic clock. So that there can only be
    > > fractional
    > > relations between them, like 1:1, 5:4, 4:3, etc. This is what is called
    > > the
    > > CPU/mem (or mem/CPU?) ratio.
    > > So what happens?
    > > When you choose one FSB frequency for the CPU, the advanced chipset
    > > settings
    > > will present you with DDR2-xxxMHz values which are indeed the FSB
    > > multiplied
    > > by the various fractions I mentionned. You can choose whichever value,

    at
    > > will, but provided you don't go too high and go over what the mem can

    do.
    > > Now, if you start by choosing DDR2-533MHz (which would correspond to a
    > > 266MHz FSB and a 1:1 ratio) and subsequently change the FSB to 300MHz,
    > > then
    > > what you will find in chipset settings for the 1:1 ratio is DDR2-600MHZ.
    > > And
    > > other values which correspond to the 5:4, etc ratios of 300MHz. If

    600MHz
    > > goes above the speed your mem can cope with, simply choose another value
    > > which, for example, would correspond to a 4:5 ratio (in this case,
    > > DDR2-480MHz).
    > > In other words, because it is the way the BIOS works (you choose an FSB
    > > frequency, and in fact a CPU/mem ratio although it is presented as a mem
    > > speed value), choose the FSB first and then adjust the chipset settings
    > > for
    > > the mem.
    > > That's how it works for my P5W DH, I guess it is the same for the P5B.
    > > Sorry I cannot be more precise on the DDR2-xxxMHz (or CPU/mem ratios)
    > > accessible, as I am not home where I use my P5W.
    > > I am not sure this is all clear?
    > >

    > Very clear, actually :)
    > As Phil put it, "overclocking is a voyage of discovery". I've discovered
    > that these motherboards with the Intel 965 chipset don't allow separation

    of
    > CPU and memory speeds. So now I'll see if I can push the memory a bit more
    > :)
    >
    > Thanks very much to both you and Phil for the information.
    >
    M. R. Carleer, Jun 28, 2007
    #6
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