How to flash a modified BIOS on ASUS Motherboards (Guide for NvStrapsReBar)

[Harveyyy101]

Hello,
I have a Z370-E motherboard and I've been having a lot of issues with flashing a modified BIOS with NvStrapsReBar.ffs
The first issue I've encountered was the Asus EZ flash bios rejecting the modified image file. This is due to the nature of the CAP file (Capsuled) and the fact that it's encrypted. I've tried other methods such as using Asus' AI-Suit software and manipulating the software/tool into thinking that it's flashing a non-modified BIOS file. The issue with that is after the BIOS is flashed, the NvStrapsReBar.ffs driver does not get loaded with the new bios.

After a lot of digging, I've finally managed to find a workaround and flash a modified BIOS with NvStrapsReBar.ffs using AFUDOS and have successfully enabled ReBar on my RTX 2060.

The solution to this problem is very simple - I'll walk you through the steps of how you can flash the modified bios file.

First off, you'll need the following tools:

1. AFUDOS
2. Rufus
3. UEFI Tool
4. A fresh BIOS image from ASUS' website

Link:
BIOS TOOLS.zip

Virustotal Scan: 4e8857723ac1cf5ef0a461725a9b8b197c5fd40af341f6a55a5ac9c1f56f7962

First Part: Prepping the USB drive

Open up rufus and make sure you have the following settings toggled/enabled:

Then click on start. This will erase and format your USB drive and make it bootable.
Once done, navigate to the USB directory and then copy the files from "Copy to USB" to the USB's root directory. There should be 2 files, AFUDOS.exe and AUTOEXEC.bat. You will get promoted by Windows, just click on replace.

Second Part: Prepping the BIOS using UEFI Tool

Open up UEFI Tool and load the CAP bios image that you've downloaded from ASUS' website.

Now each BIOS is going to be slightly different, what you're going to do is find the DXE driver region on your BIOS, you should eventually find the region that contains a lot of DXE drivers. Scroll down to the end of the region then right-click on last driver and click on "insert after" then select your NvStrapsReBar.ffs file.

The end result should look like this:

Save the image as a CAP file.

Reopen UEFI Tool and open up the modified CAP image. You can double-check if you still have the NvStrapsReBar.ffs driver. (You should have it)
Now here comes the trick, you will need right-click on AMI Aptio capsule at the top and select "Extract body" then save the bios file as a .rom file. This will essentially make it bootable using AFUDOS. Reopen the .rom file using UEFI Tool to double-check if you still have the NvStrapsReBar.ffs driver. Also, make sure the bios' file name is "bios.rom"

Now that you have your BIOS file ready, go ahead and copy it to your USB drive. You should have all these files on your USB drive:

Optional step, but it's recommended:
Load into your BIOS and "Load optimized defaults". Save it and restart your PC.

Final Part: Flashing the modified BIOS

Load into your BIOS and enable CSM, then navigate to the Boot Tab and scroll down till you find your Bootable devices. Select your USB drive without UEFI mode and hit Enter. This will load AFUDOS and it will start flashing your new modified BIOS automatically.

Once it's done, restart your PC and go into your BIOS once more and Disable CSM and Enable Above 4G Decoding and Resizable Bar, then restart your PC.

Now that you have your NvStrapsReBar.ffs loaded onto your BIOS, you will be able to use NvStrapsReBar.exe and enable ReBar.

Results:

Thank you for reading.

Regards,
Harveyyy

[terminatorul]

Thank you for this ! Looks like it will save many people

[Epikest]

doesn't work for me:

[Harveyyy101]

What's your motherboard?

[Epikest]

Asus ROG STRIX B550-F GAMING (WI-FI)

[manusalgam]

Exactly same error on TUF GAMING X570-PLUS (BIOS 5003), I've tested flashing 3405 (oldest BIOS wasn't able to flash through EZ Updater, maybe because it's not possible to downgrade from AGESA 1.2.X), but nothing changed. I've tested even corrupting bios (switching off power when upgrading) and loading mod by crashfree, but there's no luck, I'd to switch back to original 5003...

I assume we need a tool that fake the digital sign, this BIOS must be protected against non-official ROMs (maybe to avoid malicious software which can infect BIOS, what acually is pretty fine)

[zgrcn41]

rom file does not match existing bios size

[SpontaneousJ]

I got this same error unfortunately.

[BanefulDemon]

Same error, Z390-F

[zgrcn41]

Error please help

[zgrcn41]

asus pb450ma2

[NOHEATED]

UEFI DXE driver status: Not loaded (0x000000000000000A)

Still doesn`t work

Motherboard: Asus TUF B450M-PRO GAMING

ReBar in BIOS set on auto

DXE Driver configuration:
isDirty: 0
OptionFlags: 0x0002
- nGlobalEnable: 2
- skipS3Resume: 0
- overrideBarSize: 0
- hasSetupVarCRC: 0
- disableSetupVarCRC: 0
SetupVarCRC: 0x0000'0000'0000'0000
nPciBarSize: 0
nGPUSelectorCount: 0
nGPUConfigCount: 1
GPUConfig1: deviceID: 1E84
GPUConfig1: subsysVendorID: 1458
GPUConfig1: subsysDeviceID: 4008
GPUConfig1: bus: 08
GPUConfig1: device: 00
GPUConfig1: function: 0
GPUConfig1: BAR0 base: 0xF500'0000
GPUConfig1: BAR0 top: 0xF5FF'FFFF

    nBridgeCount:      1
            BridgeConfig1: vendorID:        1022
            BridgeConfig1: deviceID:        1483
            BridgeConfig1: bus:             00
            BridgeConfig1: device:          03
            BridgeConfig1: function:        1
            BridgeConfig1: secondary bus:   08

[hentzchenklein]

Same here on x299 Prime AII

[Artasdmc]

Same here. B450F.

I don't think BIOS is actually flashing even with the tool and .rom conversion.
Flashing BIOS with EZ-Flash just gives an error that it's not proper BIOS, as it probably requires signature.

I guess Asus owners are not getting this on their boards with older GPUs.

[Artasdmc]

Getting back at this saying I've even bricked my motherboard by trying to downgrade BIOS with AFUDOS, as Ez-flash does not let downgrade and mobo doesn't have a flashback feature.

Getting a programmer sent in tomorrow to reflash the chip physically with modified bios. I'll post an update if it works, or only stock untouched bios can be used.

[Artasdmc]

Forgot to get back. Physically flashed modified bios with a programmer and it doesn't work still on B450F. Tried 2 different placements.

I guess for people with Asus boards, I would just not bother with this. You'll end up bricking a board if you do try and downgrade bios forcefully.

[NOHEATED]

The worst part that it did worked once just fine the regular way, but it doesn`t work anymore

[stupable]

x570i strix ,getting error 22, tried asus ai suite trick, also did not work
i got this far tho...

[DeadGames2]

hey i may be retarted
in the UEFI tool i should find SUBType AMI Aptio or in text AMI Aptio or you mean AMI Aptio as a Intel Image etc.
yeah im retarted dont ask, would be happy for help tho