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.

[99xexp]

@Samsung_9m2zLSD I saw the link when you posted. I hope it's addressable or else this is going to get ugly ugh. Thanks again.

@userQ1zu5lCx7x Yeah, it's really spotty and if at all, not stable whatsoever. As the above guy mentioned, there is def some kind of hdmi issue. This is lame!

[psychrage]

Just tried the Club3d Ultra Speed HDMI Cable 8k 60Hz up to 10K 120Hz 1Meter/3,28 Feet cable, and it won't even do 1080p/60 without flickering and eventually going to black screen. Worst cable I've tried so far.

[99xexp]

Just an update.

HDTVTest on Youtube (from UK) has a cable called TrueHQ which seems to (sort of) resolve the issue, with him still requiring a unplug/plug for VRR. I live in California and U.S Amazon does not seem to have the above branded cable.

Just in case people are still wondering what cables have been tested including ones I tried myself:

Zeskit - no good (Although I saw someone who had one working but with no follow-up)

Fusion8K - no good

Ibra - no good

Club3d - no good

Monster - no good

Belkin - no good

Monoprice - no good

Above are obviously anectodal testing of few individuals (QLED + rtx 30-series owners are still scarce) and certain manufacturers may have an update or a newly addressed product. If anyone else has additional cables to list, or, a cable that has been confirmed working for multiple individuals, please let us know!

@userc8egQRuGvt 

Any update from the tech by any chance?

[psychrage]

UGREEN 3ft 48gbps 2.1 cable is still the best for me. But it's not perfect. It has given me the least issues.

[userUWJA5wH3tQ]

Is Game Mode or Gsync enabled?

[useryop2lhdtIz]

I noticed this when I enabled Game Mode (i.e. VRR). I found the following settings to help mitigate this a lot though:

Picture > Expert Settings > Shadow Detail: -5

General > External Device Manager > HDMI Black Level: Low

General > External Device Manager > HGiG: On

[user5XMfyxdfle]

mann I was super close to buying one Q90T but now I don't know right know I'm getting it for $1095 for the 55in but if I go LG is going to be $1499 thats a lot more 😞

[userhB3VN0ihC7]

Can confirm that the 4k120/8k60 2m or shorter cables of tersley brand off amazon work with 4k 120 on Q70T. The 3m however just flickers and drops signal. IMO it's the length of the cable, they shouldn't be selling 4k120 hdmi cables over 2m.

NOTE: this ONLY works in game mode on port 4

I still have the issue where I need to unplug the cable or wait then reset every time I start windows however...

[99xexp]

@userhB3VN0ihC7 

Thanks for the update.

Any cable over 2m...I mean that can work for some but definitely not optimal for wall mounted tv's unless your pc is standing on a tv stand.

[empythreedom]

Have you tried with the new 457.09 nvidia drivers released yesterday?  I'm curious, because I'm about to go buy this TV if it works.