Are all CPU's created equal?

Discussion in 'MacBook Pro' started by circuitt, Nov 16, 2016.

  1. circuitt, Nov 16, 2016
    Last edited: Nov 16, 2016

    circuitt macrumors member

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    #1
    My 2015 15" MBP 2.5 repeatedly (15 times in a row) gets over 13800-13900+ Geekbench score Multi core.
    Looking at the score chart, it's running as if it's a 2.8. Are all CPU's created equal ? regardless of what MHZ stamped on the chip? Back when I was building PC's (overclocking) chips varied chip by chip on how high they could be oc'ed while being stable.
     
  2. leman macrumors 604

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    #2
    Well, different CPUs (same chip spec) can have different thermal characteristics, based on impurities and chance. E.g. of two allegedly identical CPUs running at the same frequency, one can be substantially cooler. But two instances of the same chip at the same frequency should actually show very similar performance.

    What are you RAM scores?

    Edit: or even better, can you post the entire benchmark (including the detailed results)?
     
  3. circuitt thread starter macrumors member

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    #3
    IMG_1795.PNG
    I'm at work so can't run it now, but I'll do it again tonight when I get home.
    Here's a screen shot.





     
  4. cmaier macrumors G3

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    #4
    Huh? What impurities? What chance?
     
  5. leman macrumors 604

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    #5
  6. circuitt thread starter macrumors member

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  7. The Mercurian macrumors 65816

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    #7
    Impurities in the silicon crystal the chip is made from. Although 99.9999999% pure silicon, that 0.0000001% is an impurity that can affect the electrical properties at baseline. Defects in the crystal structure itself (might also have an effect at the CD of modern chips. CD = critical dimension :https://www.quora.com/What-is-the-d...nm-and-critical-dimension-in-photolithography
    And although the fabrication itself is ridiculously precise, there can still be unintentional material placed in the wrong place if everything is not working perfectly in the manufacturing process -> these are also impurities that affect electrical properties.
     
  8. circuitt thread starter macrumors member

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    #8
    Is there a CPUZ equivalent for OSX, perhaps I can monitor the CPU's actual MHZ in real time?
     
  9. cmaier macrumors G3

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    #9
    I have a Ph.D. in electrical engineering/semiconductor physics, designed microprocessors for 15 years, so I understand how doping works. But these variations result in the Schmoo distribution and are taken care of in the binning process. There will not be any substantial difference in heat generated between two identical processers, and certainly not due to any variation in "impurities" or crystal defects.
     
  10. Clint_Barton macrumors 6502

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    #10
    intel power gadget
     
  11. leman macrumors 604

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    #11
    I was obviously referring to the manufactured chips before the binning process. And it depends on how thoroughly they bin the chips afterwards. Its fairly common to have two CPUs that are sold as the same model, but show slightly different thermal characteristics and overclocking potential.
     
  12. cmaier macrumors G3

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    #12
    Except you were referring to two sold chips, one being "substantially cooler" which is very different than "slightly different thermal characteristics."
     
  13. circuitt thread starter macrumors member

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    #13
    so in layman terms, two chips spec'ed for the same MHZ, one could turbo boost higher than another?
    As in the single core clock speed seems to be on par.
     
  14. The Mercurian macrumors 65816

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    #15
    I don't think we are disagreeing here - I never mentioned heat, I was only answering the question "what are impurities?".
     
  15. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

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    #16
    I am quite sure the amount of thermal paste has a much bigger difference on thermal levels than CPU manufacturing differences, when comparing different machines.
     
  16. MacUser2525 macrumors 68000

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    #17
    That is possible but more likely that it is every chip gets its own VID or default voltage it runs at, since the power drawn (thus heat produced) is a square of the voltage applied the difference in heat can add up quickly, or combination of both. Then you could add in case that covers the cpu and it not being nice and flat between the two processors, the thermal paste below that not applied consistently ... the list can be long. Although sometimes now I am thinking about that last part they go with bare cpu no cover in laptops. Or in Apples case with the dual 2009 MP in there to mess people about on easy upgrade possibility.
     
  17. cmaier macrumors G3

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    #18
    No, they run at the same voltage. They have voltage regulators to ensure that. They have plls lock the frequency. So the only dynamic power factor that varies is the switching capacitance, but that varies much more based on what the processor is doing than on physical differences between the processors.
     
  18. MacUser2525 macrumors 68000

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    #19
    All computer boards have voltage regulators still does not change the fact that the chips that go into them have a default VID set at the factory. If you ever have the chance around a PC or three with the same motherboard/cpu model in them hit the delete key go into BIOS and you will see the VID is going to be different. Then again in the highly unlikely event that Apple is paying some monster cash to Intel for the chips they get off the same assembly line every one else gets them from for the exact binning of identical VID chips then it could be possible.
     
  19. cmaier macrumors G3

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    #20
    No, the CHIP has multiple voltage regulators that locks the on-chip VDD-VSS to whatever the cpu needs. Any VID variation is a consequence of the binning process - a chip on the left of the schmoo may be binned above its speed class and demand a higher voltage to compensate. It's rare when this is a significant factor, but more importantly devices that have this issue will also have lower static power dissipation and the higher voltage will reduce leakage, which more than compensates for any power difference caused by the voltage component of dynamic power dissipation.

    As a previous poster stated, if one is seeing a substantial heat difference under identical workloads, it has nothing to do with any supposed 'impurities' difference, but is almost certainly caused by packaging differences (different amount or distribution of thermal paste, etc.)
     
  20. terraphantm macrumors 68040

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    #21
    Yeah, but sometimes some chips really do run cooler. At least on the desktop side back when I was into overclocking and all that, I would see 10ºC differences with two supposedly identical chips, even after reseating the heatsink multiple times. The cooler running ones typically had lower default VIDs.

    Now in the case of the Geekbench scores, I suspect that more comes down to some people not closing all background processes and some people running on battery pulling the averages down.
     
  21. cmaier macrumors G3

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    #22
    In the "old" days the schmoo's were extreme, and often times they would actually DOWN bin chips frequently for the desktop. Those days are long since past.
     
  22. terraphantm macrumors 68040

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    #23
    I'm not talking that long ago. After Nehalem is about when I lost interest, but I still saw differences on that magnitude.
     

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