Basic Problem - Windows does not provide any resolution higher than 2048 x 1080 (Recommended)
I've been using this setup for some time without issue. Several months ago after a Windows update (don't recall the specifics) I found my resolution limited to 2048 x 1080 as the max possible. After spending too many hours trying everything possible to fix it , I decided to restore from backup and pause updates.
Today I decided to try a clean install of Windows 10 v1803. I installed the latest AMD driver and the driver for my monitor (Dell P4317Q), and the issue persists.
Custom desktop specs:
Radeon RX 460
Radeon Software v18.5.1
Windows 10 Pro x64 v1803 Build 17134.254
Dell P4317Q 4K LCD monitor
ASUS Z170-Premium motherboard BIOS 3801
Intel Core i7-6700K
Cooler Master Silent Pro M 1000w PSU
Corsair Vengeance LPX 32GB (4x 16GB)
UPDATE: I found if I switch 'Color Depth' in Radeon Settings from 8 bpc to 6 bpc, the additional higher resolutions are made available in Windows Display Settings. I noticed this also changes the refresh rate from 60 Hz to 24 Hz. What does this mean, where is the potential issue? Monitor, GPU driver, Windows?