MacBook Pro 16" no 60Hz 4K over usb-c in macOS, 60Hz in Windows 10

[mbonkowski]

I've just got a new MacBook Pro 16" with Radeon 5500M 4GB. I hooked it up to LG 32UD89-W 4K monitor with included USB-C cable. Initially monitor didn't work at all but after some supplemental update to Catalina it magically started working but still not properly. Now I'm getting only 30Hz 4K resolution.
In bootcamp with Windows 10, same monitor with the same cable operates in 60Hz.
DisplayPort 1.2 is enabled in monitor.
Any ideas?

 

[mbonkowski]

Anyone has an idea how to enable at least 1080p60 in HiDPI without disabling SIP?
Ideally I would like to set 2560x1440 HiDPI at 60Hz. I use this screen with Mac Pro 5.1 with RX580 at 1440p over DisplayPort.

 

[Chronos___]

You need to hold down the option-key while clicking the "Scaled" radio button to bring up the hidden part of the interface. Then you're able to change the Hz. My monitor also only displayed 60hz at first - you need to change it manually.

It should look like this:

 

[mbonkowski]

I can't change refresh rate after option clicking:

You can see all available resolutions in Switchresx screenshot.

 

[Chronos___]

I can't change refresh rate after option clicking:
View attachment 881271
You can see all available resolutions in Switchresx screenshot.

Can you click on any of the "XXX (low resolution)" options and are able to change it?

 

[Fishrrman]

I looked at the LG spec page for this display.

It says that the display has
- HDMI
- displayport
- USBc

I suggest you try a different cable.
Also, try a different PORT on the back of the display.

You're going to have to start "changing things around", and keeping notes, until you find "the combination that works".

 

[mbonkowski]

Can you click on any of the "XXX (low resolution)" options and are able to change it?

Yes, I can. Some 60Hz options are available but screen is obviously very fuzzy and with those options.

I looked at the LG spec page for this display.

It says that the display has
- HDMI
- displayport
- USBc

I suggest you try a different cable.
Also, try a different PORT on the back of the display.

You're going to have to start "changing things around", and keeping notes, until you find "the combination that works".

I bet that with USB-C -> DisplayPort cable would work as I expect. Problem is that I use DisplayPort to connect cMP5,1 and really want 1 cable connection with charging. I will try different USB-C cable first.

 

[anthoj]

Hi, I know this is an old post, but was there ever a solution to this? I am running into this exact same problem. Tried everything from holding down option key, switchresx, etc. Nothing. The same cable, same port, same monitor used to work fine but one day it just forces 30Hz. Still works fine on Windows Bootcamp. Same setup, same port, same cable.