Windows 10: 30 hz refresh not available for 4K HDMI on 2nd external monitor

I am trying to get a second external monitor to work at 4K on my Lenovo Yoga. Using 2 LG Ultrafine 27" monitors. The first one was put in service around Nov 30 of 2021 and worked fine. I was using W10 at the time. I got the second monitor in February and was still on W10. Both monitors worked at 4K along with the 14" Laptop screen until a few days ago. I bit the bullet and took the W11 dive a few weeks ago. The 4K monitors all worked fine. Recently, W11 did an update and I lost the capability of having both monitors run at 4K. One of the monitors is using a USBC to Display Port adapter and wor

:)

 

Dual Monitors Suddenly Stopped Working

OK, I figured it out a few hours after posting this. My 1st monitor was set to a 60 Hz refresh rate and apparently this Lenovo can't run a 2nd 4K monitor if the first is set to 60 Hz. Switching it to 30 Hz fixed the problem. Why this popped up after 8
months, I don't know. Weird.

 

4k display flickering on HP z24s monitor on 60 Hz with DP1.2

About a year and half ago I bought a new 4k monitor: HP Z24s.
The very first batch.

And there has been a constant disappointment. I decided to not return the display to the shop, because everything else was perfect, i.e.: colors, overall quality, price, etc.

The monitor is connected to Radeon R9 390 8G Sapphire Nitro adapter with 3 meters DisplayPort 1.2 cable.

The problem only appears when I try to set the refresh rate to 60 Hz.

On 30 Hz everything works as expected.

Sometimes, the problem is solved when I set the refresh to 30 Hz, restart
Windows 10 LTSB, and then set the refresh rate back to 60 Hz again.

The cable isn't the problem -- I tested it using another display on 60 Hz and everything worked fine. I also tried the cable using different R9 graphics cards (all from different manufacturers). The problem also persists when using another cable altogether.

I starts when I play a full-screen game, or sometimes at seemingly random times with no obvious cause..

Also, I updated monitor driver, and some time it looked good, but with every second AMD driver update I get this problem off and back.

Does anyone know how to fix this problem, or have a similar experience with this display?

P.S.: On Linux Mint 17..18, everything works like a charm -- no flickering on 60 Hz, both with opensource and proprietary drivers. However, on Mint 18 the are opensource only. And Windows, there is no difference if I set the color depth for HP monitor to 8-bit or 10-bit per color.
So bandwidth is not the issue probably.

 

4K monitor & RTX 2070

If you have an HDMI 2.0 cable, it supports 4k. It'd have to handle the actual 18 Gbps (gigabits per second), though; "high speed" cables from a couple of years ago were only rated at 10.2 Gbps.

What display are you getting through HDMI (resolution, refresh rate)
? If it's not 4k, can you switch to that in the nVidia control panel?





The monitor controls should allow you to choose which input is displayed. I hope that the monitor would automatically detect which input had a signal, but choosing it manually could help.

I'm using a DisplayPort 1.2 interface with my Samsung U28D590D. It was the only way I could get 3840X2160 at 60 Hz; the HDMI port on the monitor is only HDMI 1.4, which permits the same resolution but only at 30 Hz. The DP port is the only one I've ever used, and I don't recall whether I had to manually choose it initially or whether it was autodetected.

Best of luck.