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Cpu to Dram ratio? confused!

Discussion in 'Overclocking' started by P G, May 16, 2007.

  1. P G

    P G Guest

    Can someone please explian which is better?

    A cpu to ram ratio of 1:1 or not?

    My M/B (Abit AB9 Pro Wifi) allows various settings for the cpu to ram
    ratio, from 1:1 to 2:3 to 1:2 to 1:3 to 3:4 to 4:5 and I have no idea
    which I should be using?

    The stock setting was using 2:3 but I assuem that if you can gte the ram
    and cpu rnning at the same speed (1:1) then this will give bset results,
    is that correct?


    Thanx for any info you can pass on. I have searched for info on this on
    the net and just ended up confusing myself as sites seem to contradict
    themselves (and / or other sites)!
     
    P G, May 16, 2007
    #1
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  2. P G

    Phil Weldon Guest

    'PG' wrote, in part:
    | Can someone please explian which is better?
    |
    | A cpu to ram ratio of 1:1 or not?
    |
    | My M/B (Abit AB9 Pro Wifi) allows various settings for the cpu to ram
    | ratio, from 1:1 to 2:3 to 1:2 to 1:3 to 3:4 to 4:5 and I have no idea
    | which I should be using?
    |
    | The stock setting was using 2:3 but I assuem that if you can gte the ram
    | and cpu rnning at the same speed (1:1) then this will give bset results,
    | is that correct?

    The highest memory speed gives the best performance, even if the timings
    must be relaxed. Depending on your BIOS settings, that would be unlinking
    the CPU Clock and Memory Clock, then setting the Memory Bus or Memory Bus to
    the highest your DDR2 modules can sustain.

    See my post
    E4300 overclocking with EVGA 680i motherboard on May 14, 2007
    for SiSoft Sandra memory benchmark comparisons for DDR2 PC8500 memory at 300
    MHz Memory Clock (Memory Bus 600 MHz) and at 600 MHz Memory Clock (Memory
    Bus 1200 MHz).

    For my E4300 / EVGA 680i system this is a 1:2 CPU Clock : Memory Clock
    ratio.


    Phil Weldon

    "P G" <> wrote in message
    news:...
    | Can someone please explian which is better?
    |
    | A cpu to ram ratio of 1:1 or not?
    |
    | My M/B (Abit AB9 Pro Wifi) allows various settings for the cpu to ram
    | ratio, from 1:1 to 2:3 to 1:2 to 1:3 to 3:4 to 4:5 and I have no idea
    | which I should be using?
    |
    | The stock setting was using 2:3 but I assuem that if you can gte the ram
    | and cpu rnning at the same speed (1:1) then this will give bset results,
    | is that correct?
    |
    |
    | Thanx for any info you can pass on. I have searched for info on this on
    | the net and just ended up confusing myself as sites seem to contradict
    | themselves (and / or other sites)!
    |
     
    Phil Weldon, May 17, 2007
    #2
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  3. P G

    P G Guest

    So what you are saying is that its ok to have the memory speed faster
    than the FSB, therefore a ratio of 1:1 is not necessary.

    So, if say my FSB is at 300 and I can get the memory to run faster than
    this say a ratio of 1:2 this would equal mem speed of 600 (DDR2 speed of
    1200)

    Or likewsie if the FSb is 300 and I use a ration of 2:3 then the mem
    speed would be 450 (DDR2 speed of 900)

    etc, etc

    Is that correct?

    My memory is 2 x Gb of Crucial Ballistix DDR2 (PC2-6400C4 - 800MHz) dual
    channel kit (running in dual channel mode)

    And so far I have had it running ok at DRam clock 525 (DDR2 1050) using
    a 2:3 ratio with the cpu (cpu FSB was set to 350) but I'm a bit confused
    about which memory figure is the theoretical 800MHz max, is it the DRam
    speed of the DDR2 speed?

    Thanx

    > The highest memory speed gives the best performance, even if the timings
    > must be relaxed. Depending on your BIOS settings, that would be unlinking
    > the CPU Clock and Memory Clock, then setting the Memory Bus or Memory Bus to
    > the highest your DDR2 modules can sustain.
     
    P G, May 17, 2007
    #3
  4. P G

    Phil Weldon Guest

    'P G' wrote, in part:
    | So what you are saying is that its ok to have the memory speed faster
    | than the FSB, therefore a ratio of 1:1 is not necessary.
    |
    | So, if say my FSB is at 300 and I can get the memory to run faster than
    | this say a ratio of 1:2 this would equal mem speed of 600 (DDR2 speed of
    | 1200)
    |
    | Or likewsie if the FSb is 300 and I use a ration of 2:3 then the mem
    | speed would be 450 (DDR2 speed of 900)
    |
    | etc, etc
    |
    | Is that correct?
    _____

    This topic has been the source of much confusion, and was discussed in this
    newsgroup about six weeks ago.

    Intel Pentium class CPUs have a 'Quad Pumped' FSB. That 'Quad Pumped' FSB
    has been, for various CPU models, 400 MHz, 533 MHz, 800 MHz, or 1066 MHz
    with 1333 MHz models soon to be released.

    For these CPUs, the CPU clock is 1/4 the FSB speed, or 100 MHz, 133 MHz, 200
    MHz, 266 MHz, or 333 MHz respectively.

    DDR2 memory speed is classified in at least three ways: DDR2-800 is PC6400
    is 400 MHz clock memory. The DDR2 rating is twice the memory clock speed.
    If you use such memory with a CPU with an FSB of 800 MHz, this memory will
    run at a 1:2 CPU Clock : Memory Clock ratio if the CPU speed and Memory
    speed are both set to stock. If you have a motherboard based on the nVidia
    680i chipset you should be able to unlink the CPU Clock and Memory Clock and
    set each to whatever you will; the CPU Clock : Memory Clock ratio becomes
    whatever it will, and is a DEPENDENT variable ( the Memory Clock will only
    take certain values, but will be quite close to the number you pick. ).

    You ask the question:
    | And so far I have had it running ok at DRam clock 525 (DDR2 1050) using
    | a 2:3 ratio with the cpu (cpu FSB was set to 350) but I'm a bit confused
    | about which memory figure is the theoretical 800MHz max, is it the DRam
    | speed of the DDR2 speed?

    If your Memory Clock is set to 525 MHz then your memory is running at
    DDR2-1050, and is overclocked; 525 MHz is higher than 1/2 of DDR2-800.


    Phil Weldon

    "P G" <> wrote in message
    news:...
    |
    |
    | So what you are saying is that its ok to have the memory speed faster
    | than the FSB, therefore a ratio of 1:1 is not necessary.
    |
    | So, if say my FSB is at 300 and I can get the memory to run faster than
    | this say a ratio of 1:2 this would equal mem speed of 600 (DDR2 speed of
    | 1200)
    |
    | Or likewsie if the FSb is 300 and I use a ration of 2:3 then the mem
    | speed would be 450 (DDR2 speed of 900)
    |
    | etc, etc
    |
    | Is that correct?
    |
    | My memory is 2 x Gb of Crucial Ballistix DDR2 (PC2-6400C4 - 800MHz) dual
    | channel kit (running in dual channel mode)
    |
    | And so far I have had it running ok at DRam clock 525 (DDR2 1050) using
    | a 2:3 ratio with the cpu (cpu FSB was set to 350) but I'm a bit confused
    | about which memory figure is the theoretical 800MHz max, is it the DRam
    | speed of the DDR2 speed?
    |
    | Thanx
    |
    | > The highest memory speed gives the best performance, even if the timings
    | > must be relaxed. Depending on your BIOS settings, that would be
    unlinking
    | > the CPU Clock and Memory Clock, then setting the Memory Bus or Memory
    Bus to
    | > the highest your DDR2 modules can sustain.
    |
     
    Phil Weldon, May 17, 2007
    #4
  5. P G

    Thomas Guest

    Phil Weldon wrote:
    > The highest memory speed gives the best performance, even if the
    > timings must be relaxed. Depending on your BIOS settings, that would
    > be unlinking the CPU Clock and Memory Clock, then setting the Memory
    > Bus or Memory Bus to the highest your DDR2 modules can sustain.
    >
    > See my post
    > E4300 overclocking with EVGA 680i motherboard on May 14, 2007
    > for SiSoft Sandra memory benchmark comparisons for DDR2 PC8500 memory
    > at 300 MHz Memory Clock (Memory Bus 600 MHz) and at 600 MHz Memory
    > Clock (Memory Bus 1200 MHz).
    >
    > For my E4300 / EVGA 680i system this is a 1:2 CPU Clock : Memory
    > Clock ratio.


    I have a different result, on my P5N-E SLI, also paired with an E4300.

    I'm now running my FSB @1350 'MHz', memory in 'sync', so running at 675
    'MHz'. At CAS 3-3-3-9-1T I'm getting 6850 MB/s bandwidth in Sandra. I
    couldnt get this high numbers at 800 MHz, CAS 4-4-4-13-1T.

    An added bonus of the low CAS numbers is, of course, a lower latency...

    --
    Met vriendelijke groeten, Thomas van der Horst
     
    Thomas, May 18, 2007
    #5
  6. P G

    P G Guest

    Thanx for the explanation Phil...



    > This topic has been the source of much confusion, and was discussed in this
    > newsgroup about six weeks ago.



    Confused? you bet!, but learning more each day thanx to guys like you...


    > If your Memory Clock is set to 525 MHz then your memory is running at
    > DDR2-1050, and is overclocked; 525 MHz is higher than 1/2 of DDR2-800.



    I think I get the general idea now....I think!

    :cool:
     
    P G, May 21, 2007
    #6
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