multicore processor speeds
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Thread: multicore processor speeds

  1. #1
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    multicore processor speeds

    A friend and I have been in disagreement over the following question for the past couple of weeks, and I'm hoping someone here could give me some references to send to him. He agrues that the speed listed on multicore CPU's is the speed of all of the cores added together. I, on the other hand, insist that it is the speed of each individual core. Anyone able to help me put an end to this debate?

  2. #2
    Gonzo District BOFH westin's Avatar
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    ok.. speaking from sheer hearsay... I would agree with you... if you have a pentium core 2 duo running at 1.8Ghz, you should have the equiv of 2 1.8ghz processors running. I am sure that if I am wrong, someone will correct me promptly, which is actually appreciated. I would rather swallow my pride and learn something new, than continue with flawed knowledge...
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  3. #3
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    Quote Originally Posted by westin
    if you have a pentium core 2 duo running at 1.8Ghz, you should have the equiv of 2 1.8ghz processors running.

    then should'nt it be listed as "3.6Ghz processor"?

    like an internal combustion engine.

    eg: 1200cc engine has 3 chambers(sometimes 4) with a total capacity of 1.2 L

    and not 3/4 chamber of 1.2 L each.
    you are entering the vicinity of an area adjecent to the location.

  4. #4
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    Quote Originally Posted by bagggi
    then should'nt it be listed as "3.6Ghz processor"?
    A 2 core 1.8GHz processor isn't running at the same speed as a 1 core 3.6GHz processor.
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  5. #5
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    Hi

    Although I am not an expert, I thought to have understood as much:

    The frequency is given on a per core-basis (often that number is even
    referred to as the 'core frequency')


    reason

    It is all about performance, energy-efficiency and temperature.

    In [1, p.3] there is a graph that shows power consumption in dependency
    of the performance via over/under-clocking. You can see that a slight
    boost of performance increases the power-consumption heavily,
    a slight decrease of performance decreases the power-comsumption heavily.

    Thus, plot below, two slightly 'under-clocked' cores uses the same power
    as one single-core at maximum frequency (not overclocked!) but results in
    73% percent more performance.

    That's the 'whole' issue. Read more here at intel[2].

    Cheers

    [1] http://www.intel.com/technology/arch...ad-core-06.pdf
    [2] http://www.intel.com/technology/arch...on+tabs_engage
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  6. #6
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    Would this be dependent on the manufacturer of the processor or the architecture of the processor?

    I mean with Intel (as a hypothetical example, I don't know honestly if this is true or not) suppose they counted the frequency on each core...does that mean that the ARM11 MPCore processor would follow the same protocol?

    I honestly don't know but I'm willing to blindly guess the answer is "yes"...correct me if I am wrong (which I probably am...).
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  7. #7
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    Thanks for the help. I'm not sure if this is enough to convince him that he's wrong, but it's a start.

  8. #8
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    It is indeed the speed of each core separate. Lets use the infamous Xbox 360 as an example/reference, it uses a special multi-core processor with three cores, each having 3.2 GHz a piece. Giving it (when push comes to shove) a max of 9.6 GHz... BUT it doesn't ever use these for one specific purpose, game designers split these cores up giving certain jobs for each core; such as shadow rendering to one core etc...

    now if it was the way your friend said it is, they would play out like this... 3 cores with 1.06 GHz a piece. this just wouldn't cut it...

    Multi-core processors were an advance in technology, if it was the way your friend says it is, we would just be competing with the latest single core processors... these links will help sway your friend.

    http://www.intel.com/products/proces...e2duo+tab_spec

    http://www.intel.com/products/proces...ium4/specs.htm

  9. #9
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    The speed is for each core.

    No the speeds are not to be added together to get one large one, it doesnt work that way.

    Not sure about the xbox game developers but with pc's the OS handles the scheduling of processes on the cores.

    If you would like to know the exact details of how multicore processors works, I can recommend a book that is very boring but explains it all. I had to read the book for my advanced computer architecture class. Part of the graduate curriculum at my uni.
    Computer Architecture: A quantitative approach fourth edition
    <chsh> I've read more interesting technical discussion on the wall of a public bathroom than I have at AO at times

  10. #10
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    A simple google search yields all of the answers to your mystery, beware of the great power which lies within!

    http://en.wikipedia.org/wiki/Multi-core_(computing)

    -sp0nge
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