Okay, this one has me stumped. When switching to UEFI + GPT during a clean install, Windows is stuck in 800x600 resolution and options are grayed out. In CSM=enabled, MBR it is 19020x1080, as it should be. Installing the monitor driver does not fix it, but installing the graphics driver does...BUT there are many things I want to get done so I can make a "fresh/minimal" backup image before installing graphics drivers. At 800x600 half of Windows own dialogs are off screen (Next/OK/Apply button type stuff). Does anyone know what causes this? Maybe some UEFI/BIOS option I need to turn on? Also, the BIOS itself, or using a bootable tool, like Macrium works in 1920x1080, just not Windows. ASRock AMD B450, and B550 boards with AMD Ryzen 5 2600, and 5600 CPUs edited: Radeon RX 6600 Graphics AOC 24G2E 144Hz, 24" IPS Monitor via display port.
Sounds like the GPU is not reporting which VESA modes it supports in EFI mode. The first thing I’d look at is the GPU BIOS.
The RX 9600 is an old card. Are you using VGA? If so, DVI would be the better option. Also the GOP on that card could be buggy. There may be a newer bios/gop update for the card...
Radeon RX 6600! My bad. Not VGA, Display port > 144Hz 24" Monitor. Works fine other than that time at 800x600 before driver install. I tend to agree with Bezalel, but I have no way to tinker in the video card's BIOS. No new firmware either. Oh well! Actually, I am pretty sure my GTX 1660 Super did the same bad behavior. Might be an ASRock BIOS/UEFI thing?