Mojave can not wake up two external display using thunderbolt

Question

Level 1

8 points

Mojave can not wake up two external display using thunderbolt

I am using lg 32ul950 and lg 27ud88.

when connecting 32ul950 using thunderbolt3 cable and connect 32ul950 and 27ud88 by usb-c cable daisy chain mode. it can not wake up the display when log in to macOS .

After unplug the usb-c cable, 32ul950 works and then replugin usb-c cable ,27ud88 works.

Only can not detect both displays when two cables connected first and then boot MacBook.

There are a lot of blogs on the internet about this issue.

It has no problem when using normal usb-c cable.

Something must be wrong in thunderbolt.

maybe something is wrong and can not detect thunderbolt device when log in.

MacBook Pro 15”, macOS 10.14

Posted on Mar 12, 2019 9:18 PM

Reply

Answer 1

Top-ranking reply

melopt

Level 1

4 points

Apr 25, 2019 6:28 AM in response to Winenjou

Hi,

I had the same problem, tried everything I could remember. On my logs (Console.app) I could see the same message as in this post - https://discussions.apple.com/thread/8526209:

error 14:51:08.201133 -0400 WindowServer [ERROR] - Driver bug - rowBytes too small. Display 0x4bc00002, ioModeID 0x80001013, ioModeDepth 0x1, bytePerRow = 32, width = 1, bitsPerPixel = 32, minRowBytes = 8192 stored width = 2048. Forcing minRowBytes (possibly still wrong).

I searched for this for quite some time and there was some co-relation with MacOS versions > 10.11. This led me to SPI (see https://support.apple.com/en-us/HT204899 ).

To test the theory, I disabled SPI on my Mac (I use a non-admin user day-to-day) and it seems to have worked. I used to have problems almost every single day, and its been a week since I last had problems.

I'm not confortable having SPI disabled, but I rather be a bit less secure and have a working laptop, so for now, I'll keep it disabled.

hopefully Apple will fix this sometime.

Hope this helps

Reply

Answer 2

sterling r

Community Specialist

Mar 13, 2019 8:14 PM in response to Winenjou

Hi Winenjou,

It seems you're having trouble with your Mac coming back from sleep and waking your displays as expected. I know it's important to have your accessories behaving as expected, and I want to help.

Check out these steps that can help fro video issues:

Get help with video issues on external displays connected to your Mac - Apple Support

If you're still seeing an issue, see if the behavior continues in safe mode:

Use safe mode to isolate issues with your Mac - Apple Support

I also recommend contacting Apple Support here:

Contact - Official Apple Support

Good luck!

Thanks for using the Apple Support Communities.

Reply

Answer 3

Winenjou Author

Level 1

8 points

Mar 14, 2019 8:54 AM in response to sterling r

I have tried everything on officially help page and it didn’t solved this problem.

https://www.reddit.com/r/ultrawidemasterrace/comments/9p4vx8/help_lg_34wk95u_macbook_pro_2018/

Here is an page that a lot of people have he same issue like me,

Also this page is the problem for 34WK95U, but that display is almost the same thing like my 32UL950 except resolutions.

Since we saw a lot of people have this issue, and it only not work on he pair of Mojave and thunderbolt3, and most of us using Macbook Pro 2018 15inch .

So I think something may be wrong or there is bugs on Mojave, specially on Macbook pro 2018 15inch.

Could you please confirm this problem?

Reply

Mojave can not wake up two external display using thunderbolt

Similar questions