[SOLVED] Can't get 4k @ 120Hz with DisplayPort cable ?

[ecthelon]

I can't reach 4k 120Hz using DP kabel 1.4 (32Gbps) paired with MSI RX470 4GB Gaming X. When my monitor is in DP 1.2 mode I have just 4k 60Hz, but when I change is to DP 1.4 my monitor (in monitor settings) turns off/ goes black screen. I have tried 2 cables, the one Samsung gave me with monitor and new one to compare. When I'm in DP 1.2 mode my GPU bandwith is 5.4Gpbs and i can't change it.

Monitor works fine with HDMI 2.1 while using PS5 (4k 120hz or 1080p 120hz depends of a game).

Monitor model: Samsung LS28AG700NUXEN

Is there anything left to do to fix it or it is just GPU thing ?

 

[helpstar]

did you install the latest AMD GPU driver for your RX470?

Change the display options in windows/amd driver to 4k @120 Hz, not only in the settings of the monitor. The monitor should recognize the correct settings itself

 

[ecthelon]

I have the latest drivers. In windows I can only set 4@60 or lower. When monitor is set to 1.4 DP the screen is black. My bandwidth in AMD settings is 5,4.

 

[QwerkyPengwen]

sounds like you got a Display Port 1.2 cable.
just because a product advertises itself as 1.4 doesn't mean it is. Lots of cheaper chinese products lie and don't make the cable properly either causing it to have issues.
try a different cable like AmazonBasics perhaps.

 

[ecthelon]

I have used Samsung stock cable 8@60 and other one with 32gbps bandwidth. Situation was the same. Is it possible that my GPU is a bottleneck here? Rx470 4gb. It says is 1.4Dp ready in MSI spec.

 

[QwerkyPengwen]

If you bought this card used and it is a mining variant (or was used for mining) thinking you would get it cheap and use it for gaming, then it's possible it has a vBIOS on it that is limiting it's supported output resolutions and frame rates.

Double check that you are running in 8bpc mode not 10bpc mode for color depth.
You can only get up to 98Hz from what I can tell at 4K when using 10bpc at full 4:4:4 color and would have to reduce yourself to 4:2:2 but this would be kind of trash when it comes to text and small tiny things.

You basically have to either limit your bit depth to achieve the higher Hz output, or lower your chroma sub sampling to 4:2:2.

I would personally recommend you to just use 8bpc with full range RGB and whatnot. Your "HDR-ness" when it comes to colors and color range won't be as wide or dynamic when compared to 10bpc at full RGB and whatnot, but will be more than enough that you honestly won't see any difference unless you are into high end professional color grading work which I doubt is the case if you bought this specific monitor to also be coupled with this GPU and trying to run high refresh rates. and seeing as how you can't get the full range and effect of 10bpc anyways unless using lower refresh rates, it's kind of not really an option to bother with 10bpc.

--EDIT/UPDATE--

After doing a bit more research for you, some people reported that using the AMD software to change the resolution and refresh rate never sticks and that you need to do it from within Windows instead.
This is for the 500 series cards, but I think it could stand to reason it might be the same case as with the 400 series.

I still encourage you to start with 8bpc 4:4:4 and only go up to 10bpc 4:4:4 if it works to get you to 120hz.

 

[ecthelon]

Thank you for research and big reply. I'm gonna check it with settings you wrote. I bought this card brand new in 2016 just for gaming not mining, also my bios is up to date .