Q90R - G-sync does not work with HDMI4 port - 4k/120hz g-sync not working

[Kansilehti]

G-sync stopped working with Samsung Q90R's HDMI4 port when I upgraded to a Nvidia RTX 3080 gpu (It has two HDMI 2.1 ports).

I previously had a RTX 2070S (it has a HDMI 2.0 port) and was using Q90R's HDMI4 port + G-sync and it worked perfectly with 1440p/120hz and 4k/60hz. Q90R firmware was 1372.2.

Now with RTX 3080 I can set Q90R TV's resolution to 4k/120hz 4:2:0 (input signal plus, game mode and freesync ultimate enabled). This was on firmware 1372.2.

However when I enable G-sync and run the Nvidia Pendelum demo (or games) the TV's screen turns black and it loses the signal. G-sync enabled I've tried the pendelum demo at 4k/120hz 4:2:0, 4k/60hz RGB, 1440p/120hz RGB. All of these end up in a black screen when running the pendelum demo using HDMI4 port.

If I connect the same HDMI cable from RTX 3080 to Q90R's HDMI2 port then G-sync works at 4k/60hz RGB and 1440p/120hz RGB.

So I can't get G-sync to work at all through HDMI4 port anymore. Any ideas what could be the culprit?

I updated Q90R's firmware to 1374 from Samsung website. This did not fix the issue.

I have tried with 2 different HDMI 2.1 cables and the result is the same:
Club 3d Ultra High Speed HDMI 4K120Hz, 8K60Hz Certified Cable 48Gbps 1.5 m/4.92 ft
Hama Ultra High Speed HDMI Cable, 8K, 3.0 m

[Chayze]

Is there any update? I've finally gotten my hands on a 3070 and was looking forward to use 4k@120Hz VRR for gaming on my Q80T TV. But I can't get it to work at all. I tried every HDMI port, have enabled Input Signal Plus for them and activated Game Mode. The Nvidia Control Panel doesn't show a refresh rate option beyond 60 Hz, regardless of the resolution. Also, I can't enable G-Sync compatibility under any circumstances.
My TV has the most recent firmware 2101, Windows and drivers are also uptodate. I'm using an HDMI 2.1 48Gbps cable by Snowkids

[Ju7ez]

Hi there, it’s basically very temperamental. I have no problems with an RTX3070 and Q90R. I use the Belkin 2.1 hdmi cable (£30 roughly). 4K/120Hz. G Sync is not officially supported with this screen and will never be most likely. I found sometimes when it plays up all you need to do is power off the tv completely (wall switch) and then power back on and usually the signal recovers. You need input signal plus on and you must use hdmi port 4 as this is the only one that supports full 4K/120 but as I said it’s very temperamental. My firmware is currently 1392. Good luck.

[Udlet]

I would like to note you all the 4k120hz is now working without any issues.