QN90A: G-sync works properly @ 1440p120, but not @ 4k60, what gives?

Laytony · July 4, 2021

I bought a QN90A and while 1440p120 works buttery smooth, I thought I'd try out 4k60 but it's turning out to be a real rabbit hole. Games either crash at launch (Nioh 2) or it crashes my video drivers/gives me BSODs (Monster Hunter World).

Took me a while before finding out the root cause was G-sync/VRR. As soon as I disable it, I'm able to do 4k60 with no issues. I'm on the latest drivers, I tried two HDMI cables (one HDMI 2.0, one Zeskit 6' HDMI 2.1) and all of the ports which includes both HDMI 2.0 and HDMI 2.1. I don't think that's the issue though because all of the ports should support 4k60 VRR+HDR, which is what I'm trying to test.

Why is this the case? Are there more hardware limitations I'm not aware of? G-sync @ 1440p120 works fine for me, why not 4k60? No one on AVSforums seems to understand what my issue is, so it seems to be an isolated issue. Either my TV or my PC or... me. Idk.

Also Idk if it makes any difference but I left some pics on what it looks like in my Nvidia control panel. I'm using 4k60 under the TV format resolutions because under the PC resolutions, I'm only given 4k100 or 4k120, which means I lose HDR and am limited to 420 as I don't have an HDMI 2.1 card yet. All of the ports more or less give me the same results.

edit: Okay either some black magic happened or I'm an idiot and didn't actually test all my ports properly and I'm leaning towards the latter. Today I put it back to port 4 (the hdmi 2.1 port) just to "test it again" and what do you know, works perfectly now.

Edited July 5, 2021 by Laytony
edited for being an idiot

Ravendarat · July 4, 2021

Are all the HDMI inputs on that HDMI 2.1? And what kind of HDMI cable are you using?

Laytony · July 5, 2021

7 hours ago, Ravendarat said:

Are all the HDMI inputs on that HDMI 2.1? And what kind of HDMI cable are you using?

3/4 ports are 2.0, last port is 2.1. I've tested all of them and I'm using the certified Zeskit 2.1 cable, but I've also tried a 2.0 cable.

Stahlmann · July 5, 2021

Tbh it could be that G-Sync only works with 2.1 capable GPUs when using 4K. Also many TV's need to have the HDMI port labeled as "PC" to properly work with GPU signals. This is something you need to do in your TV settings, but i don't know how on Samsung.