iMac CPU running at maximum frequency all the time

Discussion in 'iMac' started by Khaleal, Jul 15, 2019.

  1. Khaleal macrumors regular

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    Aug 24, 2013
    #1
    Specs: iMac (27" Late 2013, i5-4570 3.2GHz, 32GB RAM, GT 755M 1GB), HS 10.13.6

    According to Intel Power Gadget, the above iMac is running at 3.2GHz constantly even while idling (with CPU utilisation of less than 1%), when it turbo-boosts it can reach 3.6GHz (but this is normal behaviour when under load).

    Is this normal? things that I tried so far: SMC/NVRAM reset, Apple Diagnostics (no errors found).
    And the CPU temperature is well under control and it rarely reaches 75 max.
     
  2. chabig macrumors 603

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    Sep 6, 2002
    #2
    According to specs, 3.2 GHz is the base frequency.
     
  3. Khaleal thread starter macrumors regular

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    Aug 24, 2013
    #3
    But shouldn't it decrease the frequency when it's idling (power saving features)?
     
  4. chabig macrumors 603

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    #4
    I don't think so. That's why it's called the base frequency. Parts of the CPU might shut down to conserve energy but the frequency doesn't slow down as far as I know.
     
  5. Khaleal thread starter macrumors regular

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    #5
    Well, I took a course in high performance computer architecture and I now for a fact that Intel CPUs decrease their frequency when they're not under load to save power (this is called power states). and I've observed this happening on my PC and Macbook Pro.

    If you have an iMac, do you mind running Intel Power Gadget and checking the frequency your CPU is running at while idling?
     
  6. mikehalloran macrumors 68000

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  7. Khaleal thread starter macrumors regular

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    #7
    please see my previous comment to chabig
     
  8. CheesePuff macrumors 6502a

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    Southwest Florida, USA
    #8
    Incorrect, only if its being thermally throttled. It's call a base clock speed for a reason.

    Processor Base Frequency describes the rate at which the processor's transistors open and close. The processor base frequency is the operating point where TDP is defined. Frequency is measured in gigahertz (GHz), or billion cycles per second.
     
  9. Khaleal thread starter macrumors regular

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    #9
    Please check this wikipedia article (under Performance States): https://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface#OSPM_responsibilities

    It's called SpeedStep in Intel processors
     
  10. chabig macrumors 603

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    #10
    In the Wikipedia article on SpeedStep, macOS is not listed as an OS that supports it.
     
  11. Khaleal thread starter macrumors regular

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    Aug 24, 2013
    #11
    macOS does indeed support SpeedStep.
     
  12. CheesePuff macrumors 6502a

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    Southwest Florida, USA
    #12
    Source?
     
  13. FredT2 macrumors 6502a

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    Mar 18, 2009
    #13
    iMac Pro: base frequency is 3.0, seems to hover around 2.0 when not doing anything (Safari and PowerGadget running).
     
  14. chabig macrumors 603

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    Sep 6, 2002
    #14
    In System/Library/Extensions there is AppleIntelSlowAdaptiveClocking.kext. That might be a clue, but there is no reason to think that your iMac isn't behaving as designed.
     
  15. Khaleal thread starter macrumors regular

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    Aug 24, 2013
    #15
    There is a kext called "IntelEnhancedSpeedStep.kext" under Extensions. a quick google search will show you many threads of people asking how to disable it (since it's enabled by default).
    Also you can see from @FredT2 comment, his iMac is decreasing its frequency while idling.
    --- Post Merged, Jul 15, 2019 ---
    Thanks for your feedback!
     
  16. chabig macrumors 603

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    #16
    I am running the latest version of Mojave and I do not have this extension. Could it be something that migrated to your system from an earlier installation?
     
  17. Khaleal thread starter macrumors regular

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    Aug 24, 2013
    #17
    I really can't understand why you don't want to believe it's supported in macOS. SpeedStep has been implemented in Intel CPUs for years, and it's supported by every major OS. FredT2 post is a live example of the feature working under macOS.
    SpeedStep is implemented and supported in macOS whether you want to believe it or not, and I don't see how this is contributing to the discussion.
     
  18. priitv8 macrumors 68040

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    #18
    Mine is also defintely clocking down, even under light load.
    Screenshot 2019-07-15 at 23.11.27.png
     
  19. chabig macrumors 603

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    #19
    I never said that. I only said that my system, which is brand new, does not have that extension.
     

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18 July 15, 2019