Throttling in New i9 MacBook Pros Appears to be Due to Power Delivery Chip

Discussion in 'MacRumors.com News Discussion' started by MacRumors, Jul 24, 2018.

  1. MacRumors macrumors bot

    MacRumors

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    [​IMG]


    A user posting on reddit and in the MacRumors forums has given a detailed account of their findings and attempts to circumvent the throttling previously discovered on the new MacBook Pro 15" models featuring the six-core i9 Intel CPUs.

    The user goes on to explain that one of the internal power limits set for the device may not be appropriate for the power draw of the CPU and identical to previous MacBook Pro models, causing the power delivery chip (known as a voltage regulation module, or VRM) to report an over power condition that forces the clock of the CPU down to scale back power. This sets up the same conditions to allow throttling to occur once again.

    These conditions may be presenting themselves due to the new six-core design of the i9 CPU featured here. While Intel increased the core count of the CPU, they did not increase the thermal design power (TDP), or the amount of dissipated power manufacturers should plan to have to cool for a proper CPU design. This is an issue because this number usually reflects normal usage, and does not account for turbo modes. It's also likely it can exceed the draw of previous four core CPUs given the similarity of clock speeds and process nodes they are featured on.

    A method for tuning this limit is provided in the post, but it requires executing a command manually or via script each time the computer boots, and would likely void the warranty if Apple technicians discovered it. Still, the user posts results of benchmarks showing successive runs with no throttling. Manufacturers will always quote likely reduced component lifetimes if used outside of their specifications, but the results appear stable, and there is no thermal throttling of the CPU, the original suspected cause of this issue.

    This fix will not address total system power draw becoming excessive, such as long sustained loads from the CPU and GPU, but it is possible Apple could issue a fix similar to the one outlined in the reddit post that is stable.

    As for whether this issue is related to the hardware design of the MacBook Pro, that is possible as well. While iFixit's complete teardown of the current 15-inch MacBook Pro is not yet available, the previous teardown reveals significant differences in the VRM chips that power the GPU and CPU of the device.

    [​IMG]
    GPU power components

    The GPU power components seen above are on the top side of the logic board near the GPU die, and thermal grease can be seen on the components, indicating that they interface with the heatsink in the device. This is in contrast to the same components for the CPU, which are featured on the rear side of the logic board with no thermal interface to the top of the package, as seen below.

    [​IMG]
    CPU power components

    Additionally, the publicly available data sheets for these parts indicate more differences that suggest their thermal profiles will be different. The International Rectifier part for the GPU features a lower thermal resistance, meaning it can better dissipate its heat to the surrounding areas (board, air, heatsink) than the Intersil part for the CPU. Additionally, it boasts a higher power efficiency, meaning it dissipates less power itself to deliver the same amount of power as the Intersil part.

    Along with the heatsink path provided for the IR parts, it's clear they will not be capable of driving the same amount of load in any sustained mode. This makes sense given GPUs can see high loads for longer periods, but this could be an area of improvement for future MacBook Pro models from Apple, especially since it has typically chosen GPUs with very similar thermal design power limits (TDPs) to the CPUs in its MacBook Pro line.

    Article Link: Throttling in New i9 MacBook Pros Appears to be Due to Power Delivery Chip
     
  2. pankajdoharey macrumors regular

    pankajdoharey

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    #3
    This is very sad, Apple is so focused on iPhones, they have forgotten the power users who actually make content and Apps for iPhones, Macs and iPads.
     
  3. jarred125 macrumors 6502a

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  4. Winter Charm macrumors 6502a

    Winter Charm

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    #5
  5. BuddyTronic macrumors 6502a

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    It's fun to pretend to be an Electrical Engineer :)
     
  6. jsalda macrumors regular

    jsalda

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    #7
    I feel this is more Intel's fault. Apple is caught in the middle, power users want the latest and greatest chips and Apple is trying to fulfill that request, but Intel's ability to deliver is lacking. This isn't just an Apple issue, any other manufacturer that uses these chips is going to have the same issues.
     
  7. aka777 macrumors 6502a

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    #8
    All Lies (Fake News)!

    Apple the great would never make such a mistake.
     
  8. Winter Charm macrumors 6502a

    Winter Charm

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    #9
    Measurements clearly show this fixes the problem. ¯\_(ツ)_/¯.

    Maybe you're just in denial. Apple ****ed up hard.
     
  9. johnalan macrumors 6502

    johnalan

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    #10

    Not really, the volatile clock ramping can be addressed by changing the power draw from the VRM.
     
  10. aka777 macrumors 6502a

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    #11
    Considering that apple basically adds an extra 0 to $ amount of everything, they should have figured this out.
     
  11. DrJohnnyN macrumors 65816

    DrJohnnyN

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  12. DNichter macrumors 604

    DNichter

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    #13
    Sounds like an Intel issue. Just another reason for Apple to drop them and begin using their own chips. Intel certainly isn't helping themselves here.
     
  13. flat five macrumors 603

    flat five

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    #14
    can somebody post or link to an example of i9 MBP clock frequency upon sustained single core usage?
    thanks
     
  14. hawkeye_a macrumors 6502a

    hawkeye_a

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    #15
    Wouldn't sustained high power usage (gaming/video-encoding) after applying the "patch" mentioned in the article cause damage due to over-heating? Or are these components throttled based on temperature independently from the chips mentioned in the article?
     
  15. DNichter macrumors 604

    DNichter

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    #16
    What other issues were there? This is the only one I knew of.
     
  16. johnalan macrumors 6502

    johnalan

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    #17
    The good news here is that this can be effectively addressed with voltage config changes.

    The machines will then be much more stable and still fast.

    The question is when will Apple initiate the change.
     
  17. IPPlanMan, Jul 24, 2018
    Last edited by a moderator: Jul 24, 2018

    IPPlanMan macrumors regular

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    #18
    Apple either knew and it said “**** it, ship it.”

    Or it didn’t know because it didn’t adequately performance test it.

    All Apple had to do was run this test to see the issue.

    Apple isn’t even trying anymore. They know we’ll buy it anyway.
     
  18. johnalan macrumors 6502

    johnalan

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    #19
    I know what you're saying but I doubt they would trade the hassle/embarrassment they got from this for the effort in testing.
     
  19. MyopiaRocks macrumors newbie

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    Aug 27, 2010
    #20
    Good if the fix is as stable as suggested, here, but I'll be a little sad if it's not a thermal issue: I was looking forward to seeing CES 2019 reveal a line of "smart ice packs" from the accessory-makers. Literally hot-swappable.
     
  20. johnalan macrumors 6502

    johnalan

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    #21
    It's not an Intel issue.
     
  21. Polymorphic macrumors regular

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    #22
    Oversights like this just give more credence to rumors that the Mac team at Apple has been gutted by resignations and retirements over the last few years.

    Once upon a time, people like me paid a premium for Apple products knowing that the beta testing had already been done.

    Now, I have a difficult time determining which Mac I find to be the least compromised and objectionable.
     
  22. Abazigal macrumors G3

    Abazigal

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    #23
    Looks like third time’s not a charm for this MacBook Pro.
     
  23. StarryNights macrumors newbie

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    NYC
    #24
    Yikes, when I order my 15in Pro in a few weeks I'll stick with the base 8750H processor.
     
  24. johnalan macrumors 6502

    johnalan

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    #25
    The processors are all affected, to varying degrees.
    It will be addressed by an Software update.
     

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