Hey guys, I need some help here. I just got a brand new PC with a 4090 and I’m using an ASUS PG32uqx monitor. The thing is, it works great with DisplayPort, but when I try HDMI, I keep getting these weird options in the NVIDIA control panel. I can either run 4K + 60Hz + RGB + Full or 4K + 120Hz + YCbCr420 + Limited. The color looks washed out, and the desktop wallpaper looks blurry like it’s in lower resolution. I’m using a 48 Gbps ANKER cable that usually works fine with my Apple TV, so I’m wondering if the cable is good enough? I’ve tried restarting, power cycling the monitor, installing the latest NVIDIA drivers, and using different cables (even an older one), but nothing’s working. I really need HDMI to work since there’s only one DisplayPort on the monitor and I need to share it between two computers. Any thoughts on what’s going on here? Any help would be much appreciated! Thanks in advance.
That’s working as intended, honestly. The monitor only supports HDMI 2.0, so those limits are because of the available bandwidth. You can’t get 4K + 120Hz + RGB/4:4:4 all at the same time on HDMI. You’ve gotta drop one to get the others to work. Dropping to 4:2:0 gives you 4K but with limited color resolution (think of it like 1080p color). It’ll look kind of washed out, and you’ll see some artifacts.
Ahh okay, that makes sense. I didn’t realize HDMI 2.0 was the bottleneck here. I guess I’ll have to stick with 60Hz for full RGB then. 
Yeah, the 4:2:0 is a trade-off, unfortunately. If you want 120Hz with full color, you might have to use DisplayPort if it’s available. Otherwise, it’s just the limitation of HDMI 2.0.
I ran into this issue too with an older HDMI cable. Try checking if your HDMI port is fully capable of 2.0 speeds. I was getting weird results until I switched to a certified 2.0 cable.
Thanks! I’ll try a certified cable and see if that makes a difference. 
I’ve had this issue with my PG32uqx too. It’s really annoying when you’re expecting full 4K at 120Hz with perfect color. If you really need the higher refresh rate and color accuracy, maybe consider a DisplayPort switch for your two computers?
Yeah, I think that’s my next option. Thanks for the idea! I’ve been leaning towards DisplayPort for the color anyway.
I’d suggest making sure your HDMI cable is rated for 48Gbps, even if it looks fine. Some cheaper cables just don’t hit the right speeds, even if they say they should. It might be the bottleneck.
Gotcha, I’ll double-check the cable. I just assumed it was fine since it works with the Apple TV, but this might be a different scenario.
I’ve had the same problem with HDMI limits. To get 4K at 120Hz with full color, I ended up getting a DisplayPort to HDMI adapter that supports HDMI 2.1. Might be worth trying if you need that setup.
I’ll look into that, thanks! Didn’t know there were adapters for HDMI 2.1 that could help with the bandwidth.