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2.2 GHz (Turbo Boost up to 3.4 GHz), 2.5 GHz (Turbo Boost up to 3.7 GHz), or 2.8 GHz (Turbo Boost up to 4.0 GHz) quad-core Intel Core i7 processor with 6 MB shared L3 cache.

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kernel_task takes up 500% of my CPU when plugging in external monitor

Since I plugged in an external monitor (via thunderbolt) my kernel_task ramps up to 500% and can’t do much on my MBP.

I researched a lot online and did the following:

  • Disabled Energy Saver - Automatic Graphics Switching on both Battery and Power Adapter mode
  • Disabled Spotlight indexing for specific types of content and also added folders like “/System” in the Privacy settings
  • Reset the System Management Controller (SMC)
  • Performed the Apple Diagnostics test (ADT - some older websites called it the Apple Hardware Test - AHT) and had no issues come from that.
  • I also use Google Drive’s “Backup and Sync” and do lots of web development with `node_modules` folders, that can have 10s of thousands of small files which I think results in CPU churn. I’ve disabled it now.
  • Shut down the computer and turned it back on. Still get same issues with the external monitor.

Now with no external monitor plugged in, every once and a while the kernel_task rises up to 300% and sometimes rarely to 500%. I’m curious if it is a software thing or a hardware thing. To me it seems more like a software thing.

I use VS Code for programming which can have a lot of background tasks, same with using node/npm which can probably be doing lots in the background. I also run iStat v6.30, and sadly I have only 21 GB of free space on my HDD (out of 500 GB…). Often I also have Slack open, and I know that’s a web app using Electron to run as a desktop application, which can be notorious for performance.

Often the fans can run high as well. I often suspect it is either due to the VS Code/npm/node/Slack thing, or kernel_task, or maybe something else I’m unaware about.

When checking memory usage via iStat, I can see that kernel_task is using 1.61 GB (oof, Firefox is using 6.36 GB).

Things I haven’t tried yet:

  • Cleaning out more free space from HDD
  • Using plain HDMI cable into the HDMI cable port
  • Taking MBP apart and cleaning any potential dust

Has anyone had similar experience with this issue and how to address it?

OS: 10.13.6

Processor: 2.5 GHz Intel Core i7

Memory: 16 GB 1600 MHz DDR3

Graphics: AMD Radeon R9 M370X 2048 MB, Intel Iris Pro 1536 MB

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Hi - I have the same problem. Have a MacBook Pro mid 2015. It works fine with no external monitor connected. When external monitor is connected, kernel_task often runs to 500 % CPU (how can that be?). The whole Mac slows down to an almost standstill, and the fans sound like an early WWII fighter plane. Have you had much luck finding out what solves this? JP

crwdns2893770:0crwdnd2893770:0crwdne2893770:0

Try this: Unplug your monitor from the AC outlet now plug in the display only into your Mac. Does that work OK then?

crwdns2893770:0crwdnd2893770:0crwdne2893770:0

Guys I'm also facing the same issue with my Macbook Pro Mid 2015. Could you please let me know if you guys were able to find the solution for this before.

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@Vishal Kalia - The issue is a damaged thunderbolt port chip on the logic board.

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@danj hiya Dan, not sure if it is the Thunderbolt, but I still haven’t tested it (lack equipment and ability). I have an additional issue where iPad or iPhone plugged in via USB can sustain a connection (the trust dialog opens and closes sporadically ). There’s definitely something wrong hardware wise and I fear it’s related to the motherboard.

@jonpp @Vishal Kalia do you have the same issue I have with USB as well?

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What helped me to solve the probem is to disable completely the Bridge Thunderbolt settings in the network configurations. I had issues for more than 4 months, disabling it brought back my mac pro 2015 to a new life.

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This was the solution for me! I literally created account to thank you ! Thanks :)

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I created an account to thank you as well. this worked 100% i spent weeks trying to figure this out.

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I have Macbook Pro 2018 15 inch and the culprit on my end is when Im plugging in my thunderbolt power adapter. As soon as you notice kernel task spikes up, unplug it. It worked on my end. Kernel Task went down fast after unplugging my thunderbolt adapter.

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Can anyone tell me what he meant with Bridge Thunderbolt Settings?

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This worked amazingly for me too. Thank you so much.

@raphael and anyone else wondering, here is what to do.

1) Open up System Preferences and click the blue 'Network' icon

2) Click the 'Thunderbolt Bridge' item on the left handside to select it

3) Press the minus sign to delete the service

4) Press apply to save changes

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I recall that the kernel_task problem is actually a feature to protect the computer, I believe from overheating but possibly other things (not confirmed). Cleaning out the dust in the computer/fans can help.

I also found some luck by moving my external monitor to the second thunderbolt port. Possibly the one it was using is defective? Just to test, I plugged in another thunderbolt peripheral into the suspect port and the kernel_task problem did recur. So maybe that is the main problem, a bad thunderbolt port.

My setup is also mid-2015 MBP 15” and this occurs primarily if I use both the screen on my MBP at the same time as the external display (Dell 24” 2K) (i.e. so I have two screens).

Peace to all.

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The Thunderbolt to HDMI adapter you are using may have damaged your Thunderbolt port.

Also check your AC power outlets and the monitor/TV is plugged in to the same outlet and the polarized plug is plugged in correctly. Its possible you zapped your port by cross-wired AC between your system and display so the ground side was hot!

Get a outlet checker to check the outlets.

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This could be the problem in my case. Is there a way to validate this, i.e. check to see if the port is damaged or not?

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The best way is to use a Receptacle Tester to test the outlets you are using for your gear. If you don't have a surge suppressor I would get one or better yet get a UPS!

With your system and display plugged in to the AC outlets but not connected together! Use a DVM to measure across the cases (ground) you should have zero volts!

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Folks this is an image of my fans before I had them cleaned.

Block Image

I faced the very same issue that you guys are facing and based on input from another forum decided to get my 2016 MPB fans cleaned out.

This made an immediate impact where when I connected my external display to the MBP.pre-cleaning, it would overheat causing the fans to spin at 6000 rpm or thereabout and the kernel_task would eat up 500%-900% of the CPU rending the system unusable.

This simple cleanup of the fans has allowed me to connect the monitor with no kernel panic anymore and even though the fans run around 5000 rpm now the CPU and GPU are running around 10 degrees cooler now.

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I'm glad you sorted this out. I reset SMC, it worked for a while. My CPU is going berserk again! 500%. I changed HDMI cable it made impact, or at least it looked like. But this morning, it is at 500% again.

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Resetting SMC helped fix me!

  • Shut down Mac
  • Hold. CTRL+OPTION+SHIFT+POWER button for 10 seconds
  • Restart Mac

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@danj and @mattscheurich I'm also facing the issue. I have a 2K display attached to:

  • MBP mid 2015
    • Processor: 2.5 GHz Intel Core i7
    • Memory: 16 GB 1600 MHz DDR3
    • Graphics: AMD Radeon R9 M370X 2048 MB, Intel Iris Pro 1536 MB
    • The CPU goes bonkers and kernel_task remains at +400%. Unplugging the Dell 2K display immediately settles it down.

I'm using plain HDMI cable for the display, it's not a thunderbolt. I'm not sure how a damaged Thunderbolt chip can be a cause here because I'm using HDMI?

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I cleaned my fans and reset SMC. Now my CPUs are not maxing out!

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when you clean the fans, how did you clean? did you blow with compressed air or removing and disassembling the fan? thanks

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