Intel Core 2 Duo Question

Discussion in 'Mac Basics and Help' started by kavi, Nov 18, 2007.

  1. kavi macrumors member

    kavi

    Joined:
    Oct 17, 2007
    #1
    Is the intel core 2 duo essentially two processors, meaning that if I had a 2.2 GHz intel core 2 duo it would be equivalent to a single processor with a speed of 4.4 GHz?
     
  2. Kaspers macrumors regular

    Kaspers

    Joined:
    Oct 7, 2007
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    the Netherlands
    #2
    No, it means you got 1 CPU, with 2 Cores, which are both running at 2,2 GHz.
     
  3. kavi thread starter macrumors member

    kavi

    Joined:
    Oct 17, 2007
    #3
    so if you have 2 cores running at 2.2 GHz isn't it like overall speeds of 4.4 GHz?

    it would definitely be more efficient than a single processor at say 3.0 GHz right?
     
  4. Shadow macrumors 68000

    Shadow

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    Keele, United Kingdom
    #4
    A Core 2 Duo at 2.2GHz = 2 cores (for all purposes of this, a CPU) of 2.2GHz but in terms of computing 2x2.2GHz != 4.4GHz. You essentially have 2 separate CPUs, which means you have two 2.2GHz CPUs. You can run 2 threads (programs) at 2.2GHz without slowdown, but not one thread at 4.4GHz.
     
  5. zakatov macrumors 6502a

    zakatov

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    #5
    just to clarify, nowdays 1 program is not 1 thread, most are multithreaded, so theoretically a multithreaded program can max out both cores (barring other bottlenecks) and come close to the performance of a 4.4GHz cpu
     
  6. Berlepsch macrumors 6502

    Berlepsch

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    Oct 22, 2007
    #6
    In some scenarios, a software task can be run simultaneously on two processors, and in this case the speed nearly doubles when you use a dual core CPU. Examples are ray tracing programs or video converters. On the other hand, some programs can only use one processor at a time. This type of software will only run faster with faster clock speeds, but of course the second CPU can run other programs in parallel.
     
  7. cube macrumors G5

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    May 10, 2004
    #7
    It's not true that most programs are multithreaded or they can max out two cores.
     
  8. chris200x9 macrumors 6502a

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    Jun 3, 2006
    #8
    first of all yes it is true most programs are multithreaded, not all, but most. second of all he said it was theoretically possible for a program to max out 2 cores, not they will.
     
  9. cube macrumors G5

    Joined:
    May 10, 2004
    #9
    Most of the desktop multithreaded programs just get it from a GUI toolkit, and all it does is preserve the responsiveness of the GUI, not distribute work.
     
  10. zakatov macrumors 6502a

    zakatov

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    South Florida
    #10
    You really have to look to find any programs that are only one thread:

    [​IMG]
     
  11. cube macrumors G5

    Joined:
    May 10, 2004
    #11
    I am not talking only about programs made by Apple.
     
  12. robbieduncan Moderator emeritus

    robbieduncan

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    Location:
    London
    #12
    Oh really? :p

    Anyway you are all assuming that two threads mean that all the work is split over the two CPUs. The normal actuality is that there is one thread keeping the GUI responsive and one thread doing whatever is time consuming. So all the real work is on one CPU.

    Yes, this is changing, but you still can't just add all the MHz together.
     

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  13. zakatov macrumors 6502a

    zakatov

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    Mar 8, 2005
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    South Florida
    #13
    You know that I meant "programs" as in something more complex than a background daemon that pops up reminders for iCal. Multiple threads can very well do "major" tasks, not just keep GUI responsive. (ie. games use one core to process physics and one for AI calculations)
     
  14. HLdan macrumors 603

    HLdan

    Joined:
    Aug 22, 2007
    #14
    I apologize for hijacking this thread but can someone please explain to me how to get the screenshot of the Finder window as shown? When I do command+shift+3 or 4 I get the background and even if I change the background to white it's obvious I have done a screenshot. This pic above looks perfect as if the Finder windows was just dragged onto the thread. Please help.
     
  15. Muzzway macrumors regular

    Joined:
    Jul 21, 2007
    #15
    Command+shift+4, then space and click on the window that you want.
     
  16. Shadow macrumors 68000

    Shadow

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    Feb 17, 2006
    Location:
    Keele, United Kingdom
    #16
    If you want more information on this, check Wikipedias articles for "Multi-Core (Computing), but it is difficult to understand (and explain for that matter) since 2x2.2 = 4.4 but in terms of CPUs 2x2.2 != 4.4. I'm going to try and explain this as simply as possible, because what we have got so far is a bit muddled.

    A program runs a series of threads on a CPU. A thread (which we'll call tasks since it makes it easier to understand) basically does a task for the program as a whole. For example, AppX might have 2 tasks: 1 to do "the actual work" and another to make the GUI (graphical user interface) still respond so the user doesn't think its crashed.

    A multi-core CPU (like the Intel Core 2 Duo, or the AMD Athlon X2) is made up of cores. A dual-core CPU obviously has 2, a quad-core CPU has 4, etc. Roughly speaking (and without getting complex and going into hyperthreading and such) 1 core can run 1 thread at any given time. So a dual-core CPU can run 2 threads at the same time.

    Understand? Good, because now it gets complicated.

    As stated, AppX has 2 tasks; T1 (Task 1) does "the actual work" and T2 makes sure the GUI does something. Now on a dual-core CPU this works because T1 runs on C1 (Core 1) and T2 runs on C2 (Core 2). Remember that each core runs at 2.2GHz. Because the tasks are separate from each other yet part of the same program, each task runs at 2.2GHz but although we theoretically have 2 tasks at 2.2GHz, we do not have 4.4GHz. A program will run at 2.2GHz, but it will be able to do 2 things at the same time without slowing down.

    This is advantageous if you run multi-threaded applications or several single-threaded applications at the same time. However, for things like games which usually are the only thing running and are not multi-threaded, it can reduce performance although total computing capacity is ≈ 2x. For this reason, games generally would run better on a 3GHz single core CPU than a 2GHz dual core CPU (having said that, games are becoming multi-threaded so this may not be true for long).

    Remember, this is a simplified version of the concept, and it doesn't go into things like hyperthreading and system busses, so take it with a pinch of salt. It is a difficult concept to understand, but once you do understand you'll wonder why it was ever difficult.
     
  17. HLdan macrumors 603

    HLdan

    Joined:
    Aug 22, 2007
    #17
    Kool, thanks, that's what I was looking for. I completely forgot about hitting the spacebar to bring up the little camera. :)
     
  18. kavi thread starter macrumors member

    kavi

    Joined:
    Oct 17, 2007
    #18
    That all makes a decent amout of sense. Thanks for all that information.
     

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