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How do you determine the bandwidth

Discussion in 'Building a new PC' started by Jinkazuya, Nov 6, 2009.

  1. Jinkazuya

    Jinkazuya Regular member

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    Bandwidth

    This is where AMD says the technology matters. More bandwidth means faster processors will be able to do more when more data comes to them faster. With DDR3 ram bandwidth now exceeding 25 GB/s, you can see that AMD is ready to accept all that bandwidth.

    Front Side Bus

    Since the FSB is 64-bits and runs between 1066 MT/s and 1600 MT/s, we can effectively determine the bandwidth.
    FSB Bandwidth
    1066 MHz 8.5 GB/s
    1333 MHz 10.6 GB/s
    1600 MHz 12.8 GB/s
    2000 (OC) MHz 16.0 GB/s

    HyperTransport

    HT recently has been running from 800 MHz from the low-end processors up to 4.0 GHz on the newest quad core processors. That is taking into account the clock multiplier but not the DDR. Since the bit-width is 32, determining the bandwidth is possible.
    HT Bandwidth Bandwidth (duplex)
    800 MHz 6.4 GB/s 12.8 GB/s
    2000 MHz 16.0 GB/s 32.0 GB/s
    3200 MHz 25.4 GB/s 52.8 GB/s
    4000 MHz 32.0 GB/s 64.0 GB/s

    BTW, is it to get the real speed or core clock speed of the AMD and Intel FSB...Do we always get the spec number of the FSB divide by 2 if it is AMD, and 4 if it is intel? For instance assuming the spec of FSB of intel is 6400, so the real clock speed is 6400 / 4 = 1600, which is the core speed of the FSB?
     
    Last edited: Nov 6, 2009
  2. sammorris

    sammorris Senior member

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    There is no 6400mhz FSB for Intel, so I'm not sure exactly what you're asking.
    For Intel's FSB, root speed is quarter the given value - 1066mhz (8.5GB/s) is 266mhz. For AMD's HyperTransport, the FSB is 200mhz, always. The HyperTransport speed is a preset value, as you say, 2000, 4000 (are the most common ones).
    Try to look past the bus bandwidth as a measure of performance - Intel CPUs actually care more about memory bandwidth, AMDs more about memory latency, and RAM bandwidth rarely exceeds 13GB/s currently anyway.
     
  3. Jinkazuya

    Jinkazuya Regular member

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    Just one word you are so darn awesome sammorris...Where did you learn all this stuff?

    Anyway, I know there is no 6400, it is just something I made up.

    1066 MHz 8.5 GB/s, this for example. How do you determine that the bandwidth is 8.5 MHz with 1066 MHz? This is what I am asking.

    BTW, what is preset value? Is the value that has been set fixed?

    I am not worried about this stuff, but really wanna learn and curious. If I really wanna build one, as you guys have already helped out, so I am not afraid to build one myself but knowledge is important here.

    Confirm your my question: Is the FSB of intel always a quarter of the given value no matter what chipset or CPU is used? Besides, the speed of Hyper-Transport? what about it? Do you know how to determine the core speed of the HT? Well...latest CPU of AMD don't have any FSB because of the HT but according to some other specs and article, even with HT, there is also FSB in some of the latest AMD CPU. Wonder if that is true.
     
  4. sammorris

    sammorris Senior member

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    1066 MHz 8.5 GB/s, this for example. How do you determine that the bandwidth is 8.5 MHz with 1066 MHz? This is what I am asking.
    That's just how it is. A Front side bus at that clock speed will have that much bandwidth - the clue is in memory speeds. Ever wonder why 1066mhz memory is called PC8500?
     
  5. Jinkazuya

    Jinkazuya Regular member

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    Just another quick question.

    Is the root speed of the FSB is always a quarter of the given value no matter how latest the CPUs are such as core 2 quad? I am not talking about icore, I am just talking about the general CPU of intel.
     
  6. sammorris

    sammorris Senior member

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    This applies to all Core 2 Chips, but nothing else.
     
  7. Jinkazuya

    Jinkazuya Regular member

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    Thanks a lot. Now that has really cleared the mystery of speed compatibility.
     

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