Question LG Oled55b9pla 3840x2160 @ 120hz

Jun 30, 2020
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This tv isn't supposed to be able to run at 4k 120hz without the yet to be released hdmi 2.1 graphics cards, but I accidently have mine running at this and want to know if it really is possible or if it must be downscaling.

Running a 2080ti through a hdmi ultra high speed 48gbps cable (bought it for future proofing), to a hdmi 2.1 port on the tv.

I have done a lot of testing and it's definitely running at 120hz, and graphics don't seem to have degraded/blurred or anything.

If I run a game that has native hdr it does cap me at 60fps.

I'm wondering maybe because i'm using a hdmi 2.1 port on the tv a long with a hdmi 2.1 cable maybe i'm getting a little over the standard hdmi 2.0 bandwith and when I add hdr into the mix it's just pushing the bandwith too far and reverts to 60fps to allow hdr to work.

https://ibb.co/9HNw5GC
 
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Yeah, but I have vsync on, so getting 120fps means the refresh rate is 120 doesn't it?
Yes, if V-Sync is working (sometimes it doesn't actually turn on when you have it selected). Since it's a TV it also may be able to run 120 Hz by using YCbCr with 4:2:0 chroma subsampling (lowering color resolution to 1080p to allow higher refresh rates) as this would still show up as 4K in the resolution selection.

You can check in the NVIDIA control panel here: View: https://i.imgur.com/XFm4Mww.png


But if you run the game in fullscreen mode the settings will revert back to what you have set on the desktop whenever you tab out of the game.
 
Jun 30, 2020
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I'm getting no screeen tearing at the higher framerates so pretty sure that v-sync is on and not just showing as on.

The desktop doesn't seem to be affected by this, its running at it's standard 3840x2160 @ 60hz with its standard colours.



What I did intially that made this 4k @ 120hz thing start happening was:

I changed to 2560x1440 and applied in nvidia control panel, then chose custom resolution.
Then created 3840x2160 @ 120hz and apllied it.
I then right clicked the desktop, display settings and went to advanced display settings.
I went into display adaptor properites, and set it to 3840x2160 @120hz.
This created a fake resolution that was only really 2560x1440, my tv showed 2560x1440 and windows thought it was 3840x2160 @ 120hz, but my desktop was noticably blurry.
But when I set my resolution back to 3840x2160 @60hz in the nvidia control panel my desktop runs at it's standard 4k 60hz, but all my games fullscreen or windowed are now able to be set to 38040x2160 @ 120fps as long as hdr is not on in game.
 
Jun 30, 2020
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I just noticed this in the nvidia control panel:



Seems my desktop still sort of thinks it's running at 120hz even though it's not.
 
Jun 30, 2020
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I was having trouble deleting my custom resolutions including the 4k 120hz one, but this preview whatever it is was always set to the last custom resolution/refresh rate I had used, regardless of how many real res+refresh rates I used.

The 4k 120hz glitch that I came across seemed to be permanent on any res+refresh I used, whether it was a lower or high resolution, even after I managed to delete the custom resolution.

So in the end I didn't trust it and have re-installed my graphics driver, the glitch is no longer happening, games are capping themselves to 60fps again and I get screen tearing if I remove v-sync and go above 60fps.
 

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