Turbo Boost 3.6GHz for both 27" models - why pay more?

Discussion in 'iMac' started by js09, Nov 29, 2012.

  1. macrumors member

    Joined:
    Sep 17, 2010
    #1
    if both the $1800 and $2000 imacs both run at 3.6Ghz, why pay for the more expensive one?
     
  2. macrumors 6502a

    Joined:
    Jun 24, 2012
    #2
    The more expensive one has a *much much much* better GPU.

    The better CPU is just a bonus at that point.
     
  3. thread starter macrumors member

    Joined:
    Sep 17, 2010
    #3
    meh.. neither have a good GPU so i don't care much about that.. I just want to know how the CPU works. are both CPU's identical after enabling turbo boost?

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    I wouldnt be surprised if both 27" models have the exact same CPU (ie.. intel 2500k). where can i find out?
     
  4. macrumors newbie

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    Nov 25, 2012
  5. lixuelai, Nov 29, 2012
    Last edited: Nov 29, 2012

    macrumors 6502a

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    Oct 29, 2008
    #5
    The 3.6Ghz Turbo Boost only kicks in if you are only utilizing 1 core which is fairly rare.

    btw the two processors are most likely i5-3470 and i5-3470S.
     
  6. macrumors regular

    Joined:
    May 28, 2012
    #6
    Where is this info from?
    Sure not from http://www.apple.com/imac/performance/ ...
     
  7. thread starter macrumors member

    Joined:
    Sep 17, 2010
    #7
    no, not really. it depends on what it's used for

    anyway, just guessing 2 of these processors are the ones used:


    i5-3470S (2.9GHz)
    i5-3470 (3.2GHz)

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    If I had to guess, the turbo boost only kicks in when utilizing all 4 cores to their max. it just idle's at the base speed. kicking in upon 1 core sounds retarded.. but maybe

    edit: just read the link above. looks like i'm probably right
     
  8. macrumors 6502a

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    Oct 29, 2008
    #8
    To quote Intel:

    The max is always single core.
     
  9. macrumors 6502a

    Joined:
    Jun 24, 2012
    #9


    I'm not sure what plane of reality you're from where you think the 680MX is "not really" a good GPU, but can I visit? It sounds weird and wonderful there!
     
  10. macrumors 6502a

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    Ireland
    #10
    :eek: The 680mx is as fast as an underclocked desktop 680mx(and Apple likely overclocked it like on their MBPs so it's probably on par) .

    Is it fun not knowing what you're talking about?
     
  11. macrumors G5

    gnasher729

    Joined:
    Nov 25, 2005
    #11
    Totally wrong. Current processors are limited by the heat they produce. More MHz = more heat. More cores running = more heat. Running fast for long time = more heat.

    An Intel processor sold as "2.9 GHz" can run at 2.9 GHz with all cores running 24/7. If only one core is running, and the computer has been idle and is therefore quite cool, only then can it run at the higher "Turbo" speed. So if you need a computer running at full speed all the time, look at the lowest quoted speed.
     
  12. thread starter macrumors member

    Joined:
    Sep 17, 2010
    #12
    I use a quadro so I should rephrase and say the GPU is not suitable for my needs. it does look like a worthwhile upgrade, though.
     
  13. macrumors member

    Joined:
    Jul 21, 2011
    #13
    Maybe not for you but there is a huge difference between the 660m and the 675mx/680mx. I'd say that for casual gaming the 675mx is needed at a minimum. Considering Apple only wants to make things even thinner this is as good as we're going to see in such a small form factor. The 660m is similar to the 6750m in my 17" MBP, which is "meh".


    You can check out everymac.com for exact CPU model numbers shipping with the new iMacs.
     
  14. thread starter macrumors member

    Joined:
    Sep 17, 2010
    #14
    interesting.

    my i7 2600k runs @ 5.0Ghz overclocked, but i *think* idle's at around 2 or 3 Ghz when "not in use". I was thinking along the same terms here, but I see what you're saying.. I wonder how it will perform. I would think that it can indeed run all 4 cores on turbo boost when needed but i guess not

    ----------

    see my post above.
     
  15. macrumors 6502a

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    Ireland
    #15
    Oops :eek: ! Sorry!

    The 680mx would be better for gaming and general usage while the Quadro would be better for Pros(Well that's how it used to be with the Quadros) .
     
  16. macrumors regular

    Joined:
    May 28, 2012
    #16
    That might be, but I was questioning your:
    "The 3.6Ghz Turbo Boost only kicks in if you are only utilizing 1 core which is fairly rare."
     
  17. macrumors 6502a

    Joined:
    Oct 29, 2008
    #17
    How so? 3.6Ghz is the Max Turbo Boost frequency listed by Intel. I already quoted the Max Turbo Boost definition.

    Btw even the Apple specs page lists "up to" which is the same way Intel describes the Max.
     
  18. macrumors regular

    Joined:
    May 28, 2012
    #18
    You stated above:
    "The 3.6Ghz Turbo Boost only kicks in if you are only utilizing 1 core which is fairly rare."
    Correct me if I am wrong, but I understood your statement as requirements for three of four cores to be idle (or near idle).
    Or what exactly did you mean by "if you are only utilizing 1 core"???
     
  19. macrumors 6502a

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    #19
    That's correct, the max turbo boost is only when using 1 core, ie all other 3 idle.
     
  20. lixuelai, Nov 29, 2012
    Last edited: Nov 29, 2012

    macrumors 6502a

    Joined:
    Oct 29, 2008
    #20
    That is precisely what I meant. The 3.6GHz will only happen when 1 core is stressed. When 2 cores are stressed the cores may run at 3.4Ghz (an example, I don't know the exact number) and so on but 3.6GHz which is listed as the max is always single core.

    Anyway you can try it yourself actually, Turbo Boost is present on nearly every Intel processor since Nehalem. Easiest way is to run something like SuperPi and watch the clockspeeds.
     
  21. macrumors regular

    Joined:
    May 28, 2012
    #21
    Got it. I thought that you said that NO Turbo Boost will get kicked on multiple cores at all.
     
  22. macrumors 6502a

    turtlez

    Joined:
    Jun 17, 2012
    #22
    I heard that a lot of the current gaming cards are out performing the quadro for professional tasks these days. Therefore the 680mx might just do that too haha. The CUDA cores for GPU rendering in gaming cards seem to be the culprit for that I think.
     
  23. macrumors 65816

    Joined:
    Dec 2, 2010
    Location:
    Germany
    #23
    When all physical and virtual cores are used at 100% each then there will be no turbo boost. It will be running at whatever speed the CPU is, 2.9, 3.2GHz, whatever.
    Turbo boost speeds up certain things, by shutting down cores and the electricity that now no longer flows to the idle cores goes to the other cores and those remaining active cores will be boosted. The highest turbo number stated anywhere will be for ONE core only. The numbers drop slightly for when two cores are boosted, three, four etc.
     

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