2020 75" Q90T HDMI 2.1 with NVIDIA RTX 3080/3090 Flicker & Disconnects

[99xexp]

Hey everyone.

I wanted to know if anyone else is experiencing problems with achieving 4k 120hz + HDR with the new RTX graphics cards on the current Q80T/Q90T models.

With number of feedbacks from a small community on Nvidia including myself, we noticed that enabling Input Signal Plus (or so called HDMI UHD Color) in order to use VRR on Game Mode results in an unstable, flickering state and will not work properly.

As a reference, it looks something like this: https://www.youtube.com/watch?v=RBc_qmA3nx4&feature=youtu.be

We have tested rigorously through the past week trying out tens of HDMI cables (we know they're not "Certified" HDMI 2.1, but are advertised as Ultra High Speed HDMI with 48gbps output), different resolution+refresh rate settings, and with the last two known updates to Samsung TV firmware (1302, 1402.1) as well. Nvidia also released two driver updates so far however, the problem doesn't seem to resolve at all.

Interestingly, Input Signal Plus on other ports besides Port 4 (hdmi 2.1) works perfectly as they should, whether it's connected via hdmi 2.0b or hdmi 2.1 cable (limited bandwidth by the port anyways), with maximum setting of 4k60hz + HDR on 4:2:2 subsampling. The problem occurs as such in the above mentioned video ONLY when Input Signal Plus is enabled for Port 4. You cannot set the resolution higher than 4k60hz without that setting.

After numerous attempts at different cable lengths and models, PSU swaps (6pin+6pin on different source), and gathering reports from the community with verified issue on all Samsung TVs, we are inclined to believe that it's likely a firmware / support issue on Samsung QLED and its proper HDMI 2.1 support.

LG CX/C9 also had a similar issue (G-Sync related) but was followed up by their team and was resolved with a firmware update to the LG TVs.

I reached out to Samsung via Twitter but was simply told to let Nvidia know lol. Not very helpful so far.

If anyone else here have had a similar experience or resolved it on your own, we would love to hear it from you.

Thanks!

Edit 10/15/2020:

We are aware that the user manual on the TV's only list 2560x1440@120hz or 4k@60hz for VRR as officially supported resolution and refresh rate. However the issue is persistent even when VRR is disabled both either via Game Mode (TV Setting) or Nvidia Control Panel.

tl;dr Port 4 currently has issues even for hdmi 2.1 bandwidth usage.

[user5gYQIW4Zrv]

hi volks

now i managed it to ran my q90t in game mode. problem was that if i turned game mode on, nvidia control panel set Ycbcr 444 instead of RGB. that causes a tv picture freeze. so i connected my notebook via teamviwer to be able change it from a 2nd pc. 

now i notice another problem.

under 4k@120hz / HDR / VRR (G Sync On)/ RGB Full / 10 Bit there is a flickering in noticeable

more then that, there is a problem with grey color tones.  you can see it clearly on my videos.

Behind the rudder padals you can see grey and when it should be darker the colour changes to black.

https://youtu.be/SjFW1T7qS_I

https://youtu.be/f4EK254WFKI

https://youtu.be/xv-0FYtaMaI

Strange thing is that on my old Displayport 1.4 to Hdmi 2.0 cable everything looks fine at 2k120hz YCbcr 4:2:0 / 8Bit. Grey colour in the same scene has more tones. 

Ofcourse i use  a ultra high speed hdmi certified cable

regards