I have R9 290, latest drivers (21.5.2) I recently bought IIYAMA G-Master GB3467WQSU which has native resolution of 3440x1440p. Windows recommends 3840x2160 which looks a little bit weird. If I force 3440x1440 I have black bars on top and bottom. After uninstalling AMD drivers, Windows recommended 1024x768, but I was able to force 3440x1440 and it looked alright. I thought that maybe some settings in Radeon Software are screwing things up, so I installed just the driver itself, but unfortunately I'm back to square one: weird looking 3840x2160 or 3440x1440 with black bars on top & bottom. Any ideas?
I get the same thing on my RX 6900 XT.
Try adjusting your custom resolutions with different base fresh rates like 60Hz 75Hz 120Hz 144Hz 200Hz or 240Hz.
Also under windows advanced display tab make sure you set the FPS rate to the max supported per the resolution you want to run.
I've had this windows 10 display feature act like a conflicting display driver before. Its a pain in the backside and likes to reset itself to 29Hz after every windows update.
Ok, I guess I figured it out: I set resolution to 3440x1440 and scaling mode in Radeon panel to full panel. Not sure if thats the "right" way to do it, but it seems to be working.
Thats part of PC building and gaming.
Figuring out the optimum settings for your particular build.
You can have the exact same build as another person and both machines can have different optimum settings. Sometime the settings can be very similar and sometimes they can vary wildly.