So I just got my LG OLED48CX and a 40 foot HDMI optical cable. I can get everything to "turn on" (HDR, 120 hz, gsync) but the TV constantly flickers on and off. I tried every option I could think of (on the TV and in the Nvidia control panel) but no dice. I'm guessing it's the cable at this point. I have another cable (6 feet) showing up today. I'll give that a shot and hopefully that works.
 
FYI, below is the cable I'm using.
https://smile.amazon.com/gp/product/B081SF1DKF/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1
 

Get the Monster 8K hdmi cable from Walmart $44 for 15-FTW3, and there is a longer one too. most likely it is the cable, makes huge difference.  I had a few high quality cables and none worked.
 
 

kring

1. You may need to cut out a rear slot divider or it blocks airflow (some other cards needed this)

I'm spoiled by the 400a, I love that I can take them all out and have a huge hole to work with there with no thin bars blocking anything.

So it looks like turning off "Instant Game Response" mode disables g-sync. So... I'm really looking forward to that firmware update.

kring
The new firmware update is out, I installed and seems fine but I won't have time for testing.  it works for US, but not EU.  If anyone wants to check but be cautious that it's probably beta and not widely available yet.
 
 

NICE! I'm downloading it now and will report back.

kring
... NVIDIA color settings and choose 32-bit, 10 bpc, yCbCr444, Limited.

So, I might be missing something, but isn't the signal coming from a PC in RGB, so wouldn't it make sense to use RGB Full instead of yCbCr444 Limited?

what do you mean by "You may need to cut out a rear slot divider or it blocks airflow (some other cards needed this)" I am not really understanding?

Its definitely not as bright as an lcd but its much better, ensure you have the oled set 100 and turn off energy saver and use high for peak brightness. 

Straykatt
Its definitely not as bright as an lcd but its much better, ensure you have the oled set 100 and turn off energy saver and use high for peak brightness. 

Turning off the automatic brightness limiter helps a lot here.

aman4672
what do you mean by "You may need to cut out a rear slot divider or it blocks airflow (some other cards needed this)" I am not really understanding?

So on the back back of your computer where the video cards Hdmi & dispay ports are located, some cases are all single slots, but the 30XX series cards are all duel slot, So you may need to cut the back of the case to make it work for a duel Slot card. Otherwise you will have a strip of metal covering the cards rear exhaust which is not good for cooling.

Dang - firmware 03.10.41 on my 65" CX still has an occasional black screen flicker spurt while crunching work units for Folding @ Home with G-Sync on. (4K 120Hz RGB 10bit Full, for those interested)

Straykatt
That’s not the recent update

Found the beta firmware works on the 65" CX as well, installed and all is well so far.

Just to chime in here, your recommended settings are not actually ideal, specifically these lines:
 
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1. For LG CX OLEDs (I have 48") you MUST go into WIN 10 advanced display settings and set resolution to 3840 x 2160, you also have to set the monitor Refresh to 120hz (defaults to 30), and enable HDR, Enable Variable refresh rate, enable hardware-accelerated GPU scheduling...  It's amazing none of this is on by default or auto-detected.  would be nice if LG offered a driver!
2. For LG CX OLEDs, in Nvidia control panel, choose Change resolution, in section 2 - choose a resolution of "PC"  3840 x 2160, 120hz refresh. Section 3, override to NVIDIA color settings and choose 32-bit, 10 bpc, yCbCr444, Limited. and apply"

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You don't have to do anything in line 1 except enable HDR, the rest will be overridden or changed by the NVidia driver once you start setting the options in line 2.
 
Also, don't use yCbCr444, the native color pattern for LCD/OLED is RGB for PC use, you're essentially putting more work on the card / system by forcing it to send a yCbCr444 signal only to be converted back to RGB by the display.  You should set it to:  32bit, 10bpc, RGB, Full.
 
It's also a good idea to set your input to PC mode, this can be done by going into the Home Dashboard, highlight the HDMI input, then selecting the settings in the top right (Press the green button), scroll down to the icon next to the label for the input, select the icon and change it to the PC icon, this will change that input to PC mode which will automatically adjust many of the picture settings for PC use.
 
Lastly and most importantly you MUST be on LG Firmware version 3.11.25 or higher for any of this to work as G-Sync and Subchroma don't work properly on prior versions with the 3x series cards.  3.11.25 isn't rolled out broadly yet so if you want it you have to install it manually (currently).  The Korean and US firmwares are the same, the Korean LG site has the firmware available for download, if you google the 3.11.25 LG CX firmware download you'll find a few places with direct links to it.
 
Once this is setup the LG and 3x series really shines... the display quality and output is truly fantastic.  Don't spend ridiculous amounts of money on HDMI cables, it's a digital signal as long as it's rated for the proper bandwidth with the right pins and gauge of wire it'll likely be just fine.  I personally use the Monoprice DynamicView Ultra 8K Premium High Speed HDMI Cable, 48Gbps, 8K, Dynamic HDR, eARC cable, the 6ft version costs a whopping $14 and it's perfect.  I use these on all 9 of the OLEDS in my house and they test solid for every video, bandwidth, and chroma test I've done so far.
 
If you want to check your signal from the card (quick and dirty), just press the green button on your magic remote a bunch of times and you'll get a Freesync overlay window that tells you your current signal.  (You want to see VRR, 3840x2160P at 120, RGB 10b 4L10) The Hz will change depending on your content.  The key here is you want to see 3840x2160P  NOT  3840x2160I or 4096x2160I.  You want progressive mode not interlaced mode.
 
There are cases where doing a Nvidia driver upgrade from an earlier version is causing issues here, (it happened to me too), the only way I could fix it was to do a full driver uninstall, reboot into safe mode and do a driver clean (while disconnected from the internet so Microsoft doesn't auto install the driver on reboot), then once back up I installed the latest driver and all of the options worked correctly, then I reconnected back to the internet and everything is happy.  (This is a last resort if you can't get your resolution to set properly with all of the noted things above).
 
If you want the more advanced version with full diagnostics, go into the TV settings menu, scroll down to the Channels tab, highlight the first option (Channel Tuning for US versions of the TV), then press 1 5 times (ie: 11111) that will bring up the host diagnostics screen.  From there scroll over to the HDMI mode, and hit Ok, this will bring up the full HDMI signal information screen.
 
Enjoy!

Veratu
Once this is setup the LG and 3x series really shines... the display quality and output is truly fantastic.  Don't spend ridiculous amounts of money on HDMI cables, it's a digital signal as long as it's rated for the proper bandwidth with the right pins and gauge of wire it'll likely be just fine.  I personally use the Monoprice DynamicView Ultra 8K Premium High Speed HDMI Cable, 48Gbps, 8K, Dynamic HDR, eARC cable, the 6ft version costs a whopping $14 and it's perfect.  I use these on all 9 of the OLEDS in my house and they test solid for every video, bandwidth, and chroma test I've done so far.

I agree with everything you said except about the cables. There are so many cables on Amazon that says they are 8k 60hz 48 Gbps and they don't work for me. I went through around 10 cables before I found one that actually works. You have to go with a decent brand, like what you did with Monoprice. Although I needed a really long cable and you're more than likely to find a cable that works if it's a short cable. I finally settled on a 30 foot optical HDMI 8k/120 Monoprice cable that was dang expensive, but it actually works.

I have an LG E9 and 3080 ftw3 ultra, I spoke with LG customer support chat yesterday and gave them my info to receive the G sync fix update. They needed my serial number and wired mac address. For now leaving G sync off, everything else works flawlessly.