Please note I've read every other thread about this issue, and none of the suggested solutions work, primarily because they either refer to older OS versions or to removing machine profiles in ACPI_SMC_PlatformPlugin.kext, a possibility which does not exist for new models (post MacBookPro8,3).

I've got a maxed out BTO mid-2015 15" MBP (2.8 GHz i7, Radeon GPU, 16GB RAM, 1TB SSD APFS FileVault turned off) running 10.13. I use it both mobile and connected to a CalDigit Thunderbolt 2 hub w/ an external 2K monitor, external drives, etc.

Primary use is audio production (Ableton Live) and software development and number crunching in Python, Pandas, etc.

This was a blazing fast machine - I could easily have a large Ableton project playing while browsing the web in Chrome and doing other things. Recently (about the time 10.13.3 came out) it slowed to an unusable crawl with the following symptoms:

  • kernel_task consuming most CPU cycles
  • fans constantly running at max
  • CPU throttling down to 800 MHz (Intel Power Gadget + iStat Menus)
  • temperatures not spiking though - CPU around 60 C most of the time
  • sometimes it will remain in this state even just sitting idle, other times it will return to normal for a bit (any activity though, even just opening Terminal and it throttles again).

To try and address this I did the following (none helped):

  • run built in Apple Diagnostics/AHT (no issues found)
  • reset SMC and PRAM
  • removed all third party Login Items, Launch Daemons, Launch Agents, Extensions, etc.
  • as suggested elsewhere removed IOPlatformPluginFamily.kext entirely - this seemed to help very briefly on reboot, but then the behaviour returned back to the above (so maybe it didn't really do anything)
  • wiped drive, reinstalled 10.13.5 clean + latest versions of my software

This leads me to the following possible diagnoses:

  • possible hardware problem (machine is covered by AppleCare, but I live in a developing country so servicing has to wait for a trip to the US)
  • exceptionally dusty/dirty inside (ordered a kit to open and clean, but internal temps are not reflecting this).
  • 10.13.3 / 10.13.4 broke something for this model (only based on timing of issue - have not had the opp to reinstall an older OS and see what happens)

In the meantime, I'd like to just be able to disable SpeedStep so I can actually use the machine - does anyone have any idea how to do it on this config?

  • I should add one thing - connecting anything (hub, FireWire or Ethernet adapter, etc.) to the ThunderBolt ports exacerbates this issue - this was not the case before.
    – tunecrew
    Jun 8, 2018 at 22:10
  • 2
    Have you tried reinstalling just the stock OS (10.13.5) on the wiped drive and installing no 3rd party apps at all, to see if you have the same experience?
    – IconDaemon
    Jun 8, 2018 at 22:33
  • @IconDaemon I've done this but w/ a minimal set of installs (Chrome, Office, Docker, Ableton) as I need those to actual work. Going to try 10.13.1 (as I still have the installer) w/ nothing else and see if I can stress it.
    – tunecrew
    Jun 8, 2018 at 22:40
  • "exceptionally dusty/dirty inside (ordered a kit to open and clean, but internal temps are not reflecting this)." So, did you clean it? The temps aren't reflecting it precisely because kernel_task is ramping up to make the machine cool itself down. That's its job.
    – Tetsujin
    Jun 9, 2018 at 5:40
  • @Tetsujin thanks, no I have not cleaned it yet. I'm aware of the role of kernel_task, however for it to kick in in the 50s/60s C when the system is mostly idle is not the expected behaviour.
    – tunecrew
    Jun 9, 2018 at 15:57


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