A quick test today showed that it was resolved by powering the machine from one of the right USB-C ports. Not knowing about this issue, I believed it was the apps that came with the webcam that were causing the fans to spin up and the machine to slow down. Oddly enough, I personally ran into this problem a few months ago while reviewing a USB-C webcam. Again moving power back to the right side, restoring State B, resolves the problem immediately.Įrgo, 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. Moving power back to the left side, restoring State A, quickly restores the temperatures and kernel_task again comes back after 3-4 minutes.

The left side temperature drops and the kernel_task goes away within about 15 seconds. State B cures the kernel_task problem by moving power from the left ports to the right. About 3-4 minutes later the dreaded kernel_task high CPU usage starts.

You can see the Thunderbolt Left Proximity temperature sensor rise quickly.

State A a USB-C hub (a mouse and keyboard, plus power) and a USB-C HDMI 2.0 adapter, both on the left side. Image via “Adam” on StackExchange showing the macOS kernel_task dominating CPU usageĪdam’s graphed test results are too big to post here, but they conclusively show that plugging in power on the right side resolves this runaway state. Suddenly the fans spin up on the MacBook Pro and CPU usage is maxed out. Which port should you charge your MacBook Pro With?Īdam discovered that if you’re charging your MBP using the left-hand ports and have other accessories plugged into that side, the computer heats up so much that a sensor - Thunderbolt Left Proximity - is alerted and a macOS process named kernel_task appears. The cause of this sudden quirk? Adam, a user on StackExchange, came up with a way to test what was happening and fully documented his results. The result? The machine would slow down while the fans on the device went into high gear. On StackExchange and other sites, MacBook Pro users documented situations where charging using the left side USB-C ports caused unusually high CPU usage. While these powerful notebooks have USB-C / Thunderbolt 3 ports on both sides, we’re going to tell you why you should charge your MacBook Pro using the ports on the right side. Photo via hardware Do you have a recent MacBook Pro? Right-side USB-C ports on a 16-inch MacBook Pro.

Macbook air usb c port