MacBook Pro showing 4 Cores!?

Discussion in 'MacBook Pro' started by Consultant, Nov 26, 2010.

  1. Consultant macrumors G5

    Consultant

    Joined:
    Jun 27, 2007
    #1
    Was just checking out the 17" MacBook Pro with i7 at Apple Store.

    Turned on activity monitor to see Flash performance on it, and noticed that the CPU usage display shows 4 graphs. What does it mean? Quad core? :confused:
     
  2. d88co88 macrumors 6502

    d88co88

    Joined:
    Dec 8, 2009
    Location:
    MN
    #3
    I think I read somewhere that the i7 "virtualizes" two cores. So that means you have to physical cores and two virtual ones. Correct me if I'm wrong.....
     
  3. Neolithium macrumors 6502a

    Neolithium

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    Wherever the army needs me.
    #4
    The Core i7's are 4 cores, it's the Core i5 that have hyperthreading, 2 physical and 2 logical cores.
     
  4. Intell macrumors P6

    Intell

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    #5
    Not all i7's are Quad Cores. I think the ones in the MBP's are two cores with HyperThreading.
     
  5. RaceTripper macrumors 68030

    Joined:
    May 29, 2007
    #6
    The i7s in the MBPs are 2 cores + hyperthreading. Intel makes a 4 core i7, but Apple doesn't use it for the MBP. A workmate has a Dell laptop with a 4 core i7, and it has a slower clock speed (like 2GHz or so). He complains about it running hot.
     
  6. Consultant thread starter macrumors G5

    Consultant

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    Jun 27, 2007
    #7
    Cool thanks. So hyperthreading makes each core act as 2?
     
  7. Eddyisgreat macrumors 601

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    Oct 24, 2007
    #8
    Kinda sorta not really yes no.

    Short story: A 2 Core HT system such as the i7 MBP will get destroyed by a 4 Core iMac w/o hyperthreading.
     
  8. aimbdd macrumors 6502a

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    East Cost
    #9
    But will do better than a 2 core system with no hyper threading. (slightly)
     
  9. dusk007 macrumors 68040

    dusk007

    Joined:
    Dec 5, 2009
    #10
    Saying 2 physical + 2 logical cores is sort of bad. It is more like 4 virtual cores running on 2 physical.

    If 2 logical cores are at full load running on top of only one physical core. Each of this logical cores is slowed down but by a little less than 50%, thus it is making one core act as two slow cores.
    Putting the same workload on these two slow virtual cores instead of one makes them finish about 20% or less.
    According to Intel they need about 5% more DIE Space for upto 25% more speed (or non at all or less, HT does hamper performance in some situations like games). AMD with Bulldozer says their double Integer Module speeds up about 80% (because most workload is Integer stuff and they basically have almost two full Integer Cores) but needs only 12% additional DIE Space per Module.
     
  10. wordoflife macrumors 604

    wordoflife

    Joined:
    Jul 6, 2009
    #11
    The i7 either has 4 physical cores or either 2 physical and 2 logical cores.

    The only benefit is the way data is transferred, because the computer thinks there are 4 physical cores.

    This is a nice way intel puts it. Click the HT tab. It applies to all processors with HT (hyper threading)

    http://www.intel.com/business/resources/demos/xeon5500/performance/demo.htm


    Intel® Hyper-Threading Technology is a performance feature on our new Intel(R) Core(TM) i7 processor and the Xeon(R) 5500 series processors. Put simply, it allows one core on the processor to appear like 2 cores to the operating system. This doubles the execution resources available to the O/S, which potentially increases the performance of your overall system
     
  11. CaoCao macrumors 6502a

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    Jul 27, 2010
  12. gnasher729, Nov 27, 2010
    Last edited: Nov 27, 2010

    gnasher729 macrumors P6

    gnasher729

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    Nov 25, 2005
    #13
    Each hyperthreading core acts either as a single core running at full speed, or as two cores running at about 60 percent of the full speed (the clock speed is the same, but they do less work per clock). So these two cores will do about 120% of the work that a single core would do. All in all, the i7 in the MBP (two cores + hyperthreading) is a bit faster than just two cores with hyperthreading, but not nearly as fast as four cores without hyperthreading.

    A real core will often do nothing because it is waiting for previous operations to finish. Say the core wants to multiply a and b, then add c. It cannot add c until the result of the multiplication is ready, and in between it's twiddling its thumbs. That's where the second virtual core comes in: When one virtual core is doing nothing, the second virtual core can do things. So while the first virtual core cannot use the "adder" in the core, the second one can use it (that's a rough model what happens, reality is a bit more complicated).
     

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