This process is pretty straightforward, but I want to clarify a few things first. The only modification made to this firmware package, which was directly downloaded from the Asus ROG website, is that I unlocked the advanced setup menu. In other words, I revealed the hidden options.
I carefully unlocked settings that I determined wouldn’t conflict with others, especially those that caused issues like a black screen after changing BIOS settings. Resetting the CMOS fixed those problems, but the settings you’re likely looking for aren’t the ones I left hidden. The hidden ones are related to PCI-Express clocks, voltage, and similar complex options, which aren’t usually beneficial for most users. I kept these locked because accessing certain advanced menus can cause the UEFI setup to freeze or break essential functions, like selecting a boot device.
I’ve double-checked the menus to ensure everything important is accessible and functional. All the settings such as…
CFG LOCK,
BIOS LOCK,
OVERCLOCK LOCK,
Shall we proceed? HOLD… No wait, proceeding… 
I’m here to share a modified UEFI firmware/BIOS for the ASUS ROG STRIX Z790-A GAMING WIFI D4 (Build 2503). This guide will walk you through the process step by step. Please ensure you follow the instructions closely for a successful flash.
Instructions:
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Prepare the USB Drive:
- Format a USB drive to FAT32 with a single partition. Ensure there are no hidden EFI partitions or any other partitions on the drive.
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Copy the Files:
- Copy the included ROM file,
SZ790AD4.CAP, to the root directory of your USB drive.
- Copy the included ROM file,
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Locate the BIOS Flashback Port:
- Power off your system completely. Locate the BIOS FLASHBACK USB port on the rear I/O panel, just below the FLASHBACK button. It should be clearly labeled and color-coded for easy identification.
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Initiate the BIOS Flashback:
- Insert the USB drive into the BIOS FLASHBACK port.
- Ensure your power supply is set to “on,” but your system remains powered off.
- Press and hold the FLASHBACK button for approximately 3 seconds. A flashing light indicates that the process has begun. Your system may light up, especially around the CPU VRM heatsink.
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Wait for Completion:
- The process can take between 1-8 minutes. During this time, do not unplug the power, press any buttons, or interfere in any way. Sit tight and let the firmware update complete.
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Finishing Touches:
- Upon completion, the system may automatically power on, or the LED on the FLASHBACK button may turn off. If the system does not power on by itself, press the CMOS clear button above the FLASHBACK button.
- Enter BIOS by pressing F7 or navigating to Advanced Mode.
Important Warnings:
- Do not attempt this process during inclement weather, especially during lightning storms, as power outages can result in a bricked motherboard. If this happens, a CH341A programmer will be required to recover, and I will not render aid with this. However, tutorials are readily available online & here on this web forum.
This modified firmware should provide all options hackintoshers, modification junkies, and troubleshooting gurus need. If you encounter any issues or have questions, feel free to reach out in this thread. Good luck, and happy modding!
Best Regards,
-MKGEN-
>>> MOD FIRMWARE LINK HERE <<<
Edit by Fernando: Thread title specified and customized