Don’t charge your MacBook Pro from the left side. Use the right side.

Ever since September 2019 I had this issue with my MacBook Pro where kernel_task would sometimes spike up to > 1000% (!) CPU load and drain my battery – even while connected to a charger.

Upon disconnecting the charger, the load would drop back to normal levels. But on reconnecting kernel_task would be at it again.


A few weeks ago I saw this tweet float by:

And yes, that totally explained my problem. As the linked StackExchange thread mentions:

High CPU usage by kernel_task is caused by high Thunderbolt Left Proximity temperature, which is caused by charging and having normal peripherals plugged in at the same time.

So the fix is simple: don’t charge your MacBook from the left side but use the right side.

Now this is not something I’d expect from a +$3000 costing machine but as the late Steve Jobs would say: “You’re holding charging it wrong” … ¯\_(ツ)_/¯

In Apple’s support article on it the function of kernel_task itself is explained in detail:

One of the functions of kernel_task is to help manage CPU temperature by making the CPU less available to processes that are using it intensely. In other words, kernel_task responds to conditions that cause your CPU to become too hot, even if your Mac doesn’t feel hot to you. It does not itself cause those conditions. When the CPU temperature decreases, kernel_task automatically reduces its activity.

So it’s basically kernel_task trying to steal CPU cycles from other processes, so that those processes don’t overheat the system.

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O.MG Cable – A normal looking USB cable that can hijack your computer when plugged in

It looks like an ordinary Lightning to USB Cable from Apple, yet it’s not: it’s got built-in Wifi and can receive payloads which get executed on the machine it’s plugged in 😱

However, let this be a reminder to never trust external cables (or USB outlets for that matter!), found USB sticks, etc.

O.MG Cable →

Using Subsurface with a Suunto Vyper on macOS (OS X)

Profile of one of the dives I did in the Maldives, displayed using Subsurface

Download the Virtual COM Port Drivers and reboot your iDevice. After that Subsurface should recognise your Suunto Vyper.

As a diver one logs all his/her dives into a paper logbook. In the paper logbook one generally notes things like the gear used, the volume of air consumed, the buddies you dove with, the diving/weather conditions, special things/animals that were encountered, a description of the dive (or a map), etc.

A photo of my paper logbook

Next to the paper logbook, modern dive computers (which divers use to keep an eye on their depth, remaining bottom time, etc.) also keep digital logs of each dive onto the dive computer itself. Over the weekend I decided to check out Subsurface, a piece of open source software for reading out scuba dives from your dive computer (created by Linus Torvalds, of all people). So I connected my Suunto Vyper to my Mac using the provided USB cable and … nothing – even though the docs state that Subsurface should automatically detect your dive computer.

Checking out System my Suunto Vyper was indeed connected, yet Subsurface would not recognize it.

“Suunto Sports Instrument”

Long story short: eventually I found a Google Groups Thread suggesting to download Virtual COM Port Drivers. One installation and a reboot later that indeed did the trick: my Suunto appeared as a mount point in Subsurface.

A mounted Vyper, yay!

In hindsight I found a note somewhere way down in the documentation about requiring drivers (“Appendix A – 17.1. Make sure that the OS has the required drivers installed”); this in contrast with earlier (and bigger) mentions in other parts of the docs of “it just works” lacking any mentions of drivers.

Subsurface →

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PlugBug is made exclusively for all MacBook Power Adapters, including current and previous models. Snap PlugBug onto your MacBook Power Adapter and you now have the first ever device that lets you charge your MacBook + iPad or iPhone simultaneously, from one wall outlet.

Clever. Very clever. For now North America only though (International version is in the making).

PlugBug →