Apologies if this has been posted in the wrong section - first time posting here.
I recently purchased a BenQ EL2870U 4K HDR monitor w/ FreeSync that's capable of 60Hz output through both HDMI 2.0 ports, but I'm getting the below results from my RX 480 - it's stuck at 30Hz.
I've lowered the HDR colour depth to 10 bpc and I've changed the pixel format to use 4:2:2 Chroma sub-sampling but it doesn't seem to fix anything. I'm using an HDMI 2.1 cable that states it's backwards compatible to older HDMI versions.
Any ideas on how to resolve this?
EDIT: I've gone to Advanced Display Settings and made sure that the Refresh Rate under 'Monitor' was set to 60Hz (it wasn't before). I've also tried to amend the listing under 'Adapter' to '3840 by 2160, True Colour (32 bit), 60 Hertz' but it seems to automatically revert back when I next go into it.
EDIT2: Similar to the tests above, I've tried changing the resolution on the display and ended up with the following results:
1080p and 1440p: outputs at 60Hz without issue
1800p: automatically reverts back down to 50Hz
4k: continues to revert to 30Hz
Horizontal Timing Total - 4400
Horizontal Timing Display - 3840
Horizontal Timing Front Porch - 176
Horizontal Timing Sync Width - 88
Vertical Timing Total - 2250
Vertical Timing Display - 2160
Vertical Timing Front Porch - 8
Vertical Timing Sync Width - 10
Horizontal Timing Polarity - Positive
Vertical Timing Polarity - Positive
Interlaced/Progressive - Progressive
G.Pixel Clock (KHz) - 297000
G.Refresh Rate (Hz) - 30
Current HDCP Status - Disabled
Current Link Settings - Not Available
You didn't mention the Manufacturer of your RX480 but Sapphire's RX480 - 8GB GPU card does support 4K@60 Hz : https://www.cnet.com/products/sapphire-radeon-rx-480-graphics-card-radeon-rx-480-8-gb/
Try using your Display Port on the RX480 to the Display Port input on your monitor and see if your get 4K@60Hz.
Try resetting Radeon Setting to factory default and turn off Freesync and HDR in Windows Setting and see if you are able to get 4K@60Hz with both of those settings disabled temporarily.
Your BenQ does support 4K@60Hz. Make sure you have the latest Windows 10 Monitor driver installed.
From your BenQ Manual concerning HDR:
BenQ mentions something about a Resolution file you can download from their website. Download the Resolution file and see if that fixes your issue from here: https://www.benq.com/en-us/support/downloads-faq/products/monitor/el2870u/manual.html
NOTE: the only thing I couldn't find is whether the 4K@60 HZ is supportrd on both DP and HDMI on your monitor or just on the DP port.
EDIT: I do know that if you are using an HDMI adapter some adapters doesn't support 4K@60 HZ output but only at 30Hz.