CPU Usage %

Discussion in 'iMac' started by Markleshark, Nov 21, 2006.

  1. Markleshark macrumors 603

    Markleshark

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    Carlisle, Up Norf!
    #1
    So, basically, its just one of those things I don't know...

    I was wondering if someone (Pretty broad question, I know) could explain how CPU usage percentage works. Coz I have a CoreDuo Mac Mini, all that I understand, one processor, 2 cores, etc, etc. So will that show as 200% CPU, or is that for 2 physical processors?

    Just an explanation would be nice, just one of those things I've not really got round to understanding.

    Cheers Peeps
    Mark
     
  2. robbieduncan Moderator emeritus

    robbieduncan

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    #2
    2 cores is the same as 2 physical processors in this case, so yes max is 200%.
     
  3. dextertangocci macrumors 68000

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    Apr 2, 2006
    #3
    Yes, in activity monitor you'll see 2 graphs showing the processor percentage used per core:)
     
  4. LeviG macrumors 65816

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    #4
    um, I was under the impression that it was only 100% total (admittedly more windows based on this)

    each cpu/core is equal to 50% of the overall performance of the system/cpu. The individual graphs show the percentage of that 50% that is being used on each core/cpu.

    So say you have 1 core running at 25% and the other at 50% use the overall use would be (25% of 50% = )12.5% and (50% of 50% =) 25% which would give a 37.5% overall cpu percentage.

    If both cores/cpus are running at full speed (ie 100% each) then the overall cpu percentage would only be 100% due to the fact that 100% performance for the cpu/cores would be the combined performance of the cpu/cores.


    Maybe macs register the information differently to pcs but the above is my understanding of it.
     
  5. Nutter macrumors 6502

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    #5
    I don't know how it works in Windows, but in Activity Monitor 100% does represent only a single CPU core, as robbie said.
     
  6. robbieduncan Moderator emeritus

    robbieduncan

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    #6
    OSX is a Unix so follows the long established Unix standard process of each core or CPU being 100%. So on a Mac Pro you can have 400%!
     
  7. wmmk macrumors 68020

    wmmk

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    #7
    or 800% if you're good at doing hardware mods;)
     
  8. robbieduncan Moderator emeritus

    robbieduncan

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    #8
    And have a lot of cash :D
     
  9. Markleshark thread starter macrumors 603

    Markleshark

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    #9
    Thanks for the replies guys, as I say, just something I never got my head around.

    However, when I take a picture of AM, I still get 2 graphs, for both cores, but the usage percentages only add up to 100%. Will I see more percentage as I do more CPU intensive things (Video Encoding, etc)
     

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  10. LeviG macrumors 65816

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    #10
    windows has two ways of displaying the graphs
    1) single graph showing current cpu usage total (100%) with a single window showing history/current cpu usage.

    2) single graph showing total cpu usage (100%) and 2 or more graphs showing cpu history/current cpu usage

    the history/current cpu has no numbers saying actual amount though.

    EDIT: although this is only in task manager other programs available display the same info slightly differently
     
  11. ATD macrumors 6502a

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    Sep 25, 2005
    #11
    Here's Maya rendering with mental ray on a quad. The bottom bar is a utility that shows total use of each cpu.
     

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  12. Markleshark thread starter macrumors 603

    Markleshark

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    #12
    Awesome stuff.

    Could you tell me where to get that Menu Bar add on, pretty please.
     
  13. ATD macrumors 6502a

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    Sep 25, 2005
    #13
  14. Markleshark thread starter macrumors 603

    Markleshark

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    Carlisle, Up Norf!
  15. jsw Moderator emeritus

    jsw

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    Location:
    Andover, MA
    #15
    Keep in mind that you've only got it set to show your processes, so those of the system and any other logged-in users won't show. Set it to "All Processes" (top rightdrop-down) to see them all.
     
  16. wmmk macrumors 68020

    wmmk

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    #16
    heh. i was going to say that!
     

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