I have an external LG 27UD69P-W monitor connected (via HDMI) to my late 2013 MacBook Pro, which causes the CPU usage of the Mac to go extremely high (
kernel_task > 400%, sometimes much higher even), with the fan running very fast. (The computer is so sluggish that even the cursor does not move smoothly, often.)
Some things I've noted:
- SMC reset doesn't help.
- Safe mode doesn't help.
- GPU usage is very low (almost zero) when monitor is connected. Is this to be expected?
- Occasionally I can connect the monitor and still have a usable computer (< 50% CPU usage) for 5 or 10 minutes, but that's it.
- Monitor works fine with another MacBook.
What could be the issue here? A troublesome kext perhaps? Any suggestions?
Here's my system log for when I plug in the screen and a couple of minutes after, while the computer is running sluggish / high CPU usage. Notable are the following sorts of events:
kernel Currently unsupported feature requested
kernel DisplayPipe Capabilities are not supported on offline Fbs
com.apple.AmbientDisplayAgent Invalid display 0x1b5671a5
Here's a "normal" system log for a few minutes while the monitor is not plugged in.