60hz on LG Ultrafine 4K with Macbook Pro 2016

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Level 1

8 points

60hz on LG Ultrafine 4K with Macbook Pro 2016

I'm struggling to get 4096 x 2304 at 60hz using the hardware mentioned.

It works intermittently. If I unplug and replug the monitor cable, it sometimes comes back in 60hz. But then it reverts to 30hz after waking from sleep.

I've installed SwitchResX and the 60hz resolutions are just missing sometimes - see https://www.evernote.com/l/AFUEaitsECJFb59g2P7zgyefBMlpgAOLw9U

I could be imagining it, but I think it was running at 60hz reliably before my recent High Sierra upgrade.

Apple say 60hz is supported on my hardware here: https://support.apple.com/en-us/HT207447

I suspect my cable is bad. I'm using the one that came with the monitor. I've ordered another, so I'll see if that fixes it. (https://www.amazon.com/gp/product/B01CEFESRO/ref=od_aui_detailpages00?ie=UTF8&ps c=1)

I notice that the shorter cables have higher bandwidth ratings, so hopefully this 3 foot cable is better than the 8 foot cable that ships with the monitor.

Has anyone else experiences this problem? Any advice?

MacBook Pro (13-inch, Late 2016, 2 TBT3)

Posted on Nov 21, 2017 8:19 AM

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Answer 1

Nov 24, 2017 6:54 AM in response to graemian

> restart your Mac in safe mode to reset the display resolution to defaults.

That is a general suggestion of how to recover from setting your only screen's resolution to something completely out-of-bounds, and the picture disappears. You are stuck with no display, EXCEPT:

Restart in Safe Mode, and the system checks the disk (adding five minutes to the start up process) then loads the absolute minimum of Apple-only extensions. It takes defaults for everything possible, ignoring your settings.

The screen comes back to life using a default resolution, but its stored resolution is not automatically changed. Screen refresh will be quirky and slow, but should be functional. Any changes you make while in Safe mode will "stick" in Regular mode.

So you reset the screen resolution to something sensible, and the change is made, "live". When you restart in regular mode, your screen keeps the changed resolution and works again.

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Answer 2

AppleJoe

Community Manager

Nov 22, 2017 5:19 PM in response to graemian

Hi graemain,

It sounds like your refresh rate is not staying consistently at 60Hz when the computer wakes from sleep. We would recommend the troubleshooting in the following article about issues with external displays:

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

restart your Mac in safe mode to reset the display resolution to defaults.

If starting in safe mode doesn't resolve the issue, reset your Mac's NVRAM and SMC to reset the video ports on your Mac to their defaults.

Take care!

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Answer 3

graemian Author

Level 1

8 points

Nov 24, 2017 6:06 AM in response to AppleJoe

Thanks for the advice. I tried resetting the NVRAM and SMC and it looks good so far.

I unplug my Mac from the external display quite often. I'm nervous that I'll be back at 30hz in the near future as a result of this. Do you think the reset is a permanent solution? I find it hard to believe that somehow the video ports got into a funny state which can only be fixed by reset?

Also, how exactly would you do the following?

> restart your Mac in safe mode to reset the display resolution to defaults.

I only restarted in safe mode after doing the resets, so I don't know if this would have worked. As best I can tell, there's nothing to actually do except restart in safe mode, then restart back into normal mode?

FYI: before doing the resets, I tried 2 new cables, but that didn't solve the problem:

- Belkin USB-IF Certified USB-C to USB-C Thunderbolt 3 Cable, Compatible with Thunderbolt 3 and USB 3.1 (3 Feet)

- Belkin Thunderbolt 3 Cable (USB-C to USB-C), 100 Watts (1.6 Feet / 0.5 Meters) - F2CD084bt0.5MBK

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Answer 4

graemian Author

Level 1

8 points

Nov 24, 2017 12:57 PM in response to graemian

Argh, I just got 30hz again after waking from sleep, so resetting NVRAM and SMC didn't fix the problem. I'm thinking of downgrading to Sierra...

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