For nearly the last 20 years I’ve been working on a laptop configuration with the laptop off to one side, propped open, and attached to a big external display. The external display is my main desktop, and the open laptop is secondary. I use an external keyboard and trackball to drive the thing.
A month or so ago I moved the laptop — currently a 2015 MacBook Air, which I bought new — to the FRONT of the display. That meant the laptop screen was below the big monitor, and I was typing on the laptop’s built-in keyboard and using its built-in trackpad. I LOVED that. I got much better use out of the laptop display.
But I noticed it was running slow. I opened Activity Monitor and found a process called kernel_task was using up a ton of memory and CPU. What the hell is kernel_task, I asked myself. Google to the rescue.
kernel_task is a fake process — it intentionally soaks up processor resources to slow your Mac down and keep it cool.
I could hear the fan running loud.
Aha, I said to myself.
Elsewhere on the Internet (I’ve lost the link) I saw a suggestion that using a big external display and the onboard display together could make a MacBook Air overheat. That’s lots of pixels for the Air’s relatively wee processor to draw.
Another potential cause of overheating: Running the MacBook Air on a surface that does not provide adequate ventilation.
I was doing all of that. So I moved the MacBook back to its stand, and kept working.
This morning, I noticed the MacBook was running slow and hot again, even while I had it on a stand with adequate ventilation. So I closed the clamshell on the MacBook and am just using the big display as my only monitor. The MacBook performance improved a little right away, and now the fans are off and the MacBook is running pretty well.
I’m about to take my exercise break. I’m going to shut down the Mac and let it cool completely while I’m out. Then I’m going to try one other thing: I bought a keyboard condom back when I was using the MacBook keyboard as my primary input; it’s possible that the condom is blocking air flow and causing the MacBook to overheat. I’ll try getting rid of that and see if I can at least get the two-display benefits by keeping the MacBook open and to one side while I work.
Although on the other hand there’s something to be said for the focus of having just one display.
Update Sunday 4/8: Problem solved (I think).