Question Update bios

How do I update the bios on a asus z790 p without a screen.
If this is your motherboard;
then you can't flash the BIOS without a screen or any form of a display output from the platform. You will need to drop in a processor preferably from the 13th Gen Intel processor that's not an F SKU so you can work with the iGPU, one single stick of ram in slot A2 and then power the system with a PSU. You won't need storage or a discrete GPU but you will need a spare system that's able to connect tot he internet to download the latest BIOS version off of Asus's support site.

Had you a motherboard with the BIOS FlashBack button on the rear, then you merely needed a PSU, no need for a display.