I just got this Asus 1080p monitor and I've connected my Mid-2014 13-inch rMBP (2.8GHz Intel Core i5, 16 GB of memory, Intel Iris 1536 MB Graphics, running El Capitan 10.11.6) to it via HDMI. The Macbook is in a vertical dock in closed clamshell mode. It's plugged in with the screen off, and I've got a cheap Anker keyboard and Magic Trackpad 2 connected to it. When it's plugged in via HDMI to the monitor, whether the monitor is on or off, the CPU load is constantly at 100% with the fan spinning rather loudly.
Activity Monitor shows the CPU load is almost all from kernel_task, and ~3% user, ~97% system.
When I unplug the HDMI cable, the fan stops going and CPU usage drops immensely.
Is this behavior from my Macbook as unusual/harmful as I would think, and what can I do about it?
Edit: Google Chrome and Xcode are running significantly slower on the monitor than they do on my Macbook itself.
Edit 2: As soon as a posted this, my fan stopped whirring so rapidly (though CPU usage did not drop from 100), and Activity Monitor showed that CPU usage is about 15% each from 5 different
Google Chrome Helpers (?) and only 1% from
kernel_task. What on earth?