I try to flash my modified BIOS for a Asus AM1M-A with afudos.exe 3.07.01. "afudos.exe file.rom /P /B /K" fails with "Security verification failed", so I tried "afudos.exe file.rom /GAN", but afudos.exe doesn't recognize this option. Instead it shows the help text with all options.

So how do I flash my modified BIOS? This mainboard doesn't support USB BIOS Flashback.

EDIT:
I found the older version of afudos.exe which does still support the /GAN switch (from [Guide] How to Flash a Modded BIOS on a ASUS Z97 Motherboard). When I try to flash the modified BIOS, afudos complains about an incorrect ROM size. And indeed, it is right: my modified BIOS is 8,390,656 bytes, while a saved version (with afudos.exe /o) is 8,388,608 bytes. So why does my modified BIOS grow in size?

That tells us two things, first do not try to further flash this modified BIOS. Second, the first flash may or may not have failed due to needing /GAN support. It's possibly due to bad modification, but may not be limited to that alone.
Why your BIOS changed size, due to method used, tool used, or mistake. If you need help modifying a BIOS please make a thread with all the details (mods you need done, BIOS links etc) and someone will help.

Damn, didn't recognize that was 2kb difference, thanks @plutomaniac

After I modified the saved version of the BIOS (created with afudos.exe), I re-flashed this one and it worked fine. :)

Hello guys,

I am trying to flash an Asus P8Z77V-LE motherboard with its latest vanilla BIOS with the NvmExpressDxe_4.ffs module, based on this article:
[Guide] How to get full NVMe support for all Systems with an AMI UEFI BIOS
It is the extracted module, the BIOS image is the same size after modding as before.

The Asus flashback feature doesn't work for me, the flash indicator LED remains light, so I am trying this alternative solution described in this forum.

I have succesfully managed to make a .ROM backup, inserted the module as well.
Unfortunately I get this error:

$PATH\>AFUWINx64.EXE modded.rom /P /B /K
+---------------------------------------------------------------------------+
| AMI Firmware Update Utility v3.09.03.1462 |
| Copyright (C)2017 American Megatrends Inc. All Rights Reserved. |
+---------------------------------------------------------------------------+
Reading flash ............... done
- ME Data Size checking . ok
- FFS checksums ......... ok
1e - Error: Secure Flash function is not supported on this file.

Ufortunately there isn't any /GAN option either. :(

What do you think, gow can I proceed to flash this BIOS?

Try more smaller USB sticks, with nothing but the BIOS file on them, and rename the file to asus recovery name (P8Z77VLE.CAP). You did already extract from capsule before modifying correct?

Did you try the other method, with AISuite
[Guide] How to flash a modded AMI UEFI BIOS

For /gan you need special ES engineer versions of AFU. But, better flashing method is to use Intel Flash Programming Tool (FPT)

To get around the AFU issue with secure flash, remove the BIOS from the capsule using UEFITool, or using the /capsule switch (You must remove /K switch from your command to use /capsule, it only allows /p /b /n /e )
But again, I would use FPT or get flashback working with proper file name mentioned above and possibly different USB stick, but you may not need that once you rename the file and file must be in root of FAT32 formatted USB Drive

Thank you very much! Your first sentence have solved everything. :)
The image file was called P8Z77-V-LE-ASUS-1104.CAP, as it was the latest downloaded vanilla BIOS image.
Assumed this was the correct name, though I have read about the naming conventions.
Obviously not that thoroughly.

Now testing phase.
Thank you again!!! :)

Cool you got it sorted out without further delay! Thanks for the beer, I'll have two
About the names, sometimes you need to use the "Recovery" name, not always though, but that's what I mentioned above is this boards recovery name.

Hello guys,

I am going to add NVME driver for dell old desktop. The bios file (Dell PC) that I extracted is .BIN file and Is that same as .ROM file ?

Thank you

Yes, same for this purpose. You want the PS-A13.bin file

Hello,
Please take this guide out that forum from the otherwise good site.
I came here, because I made a modified cap (with NVMe) module for ASUS M5A99X EVO R2.0. Everything went fine, but unfortunately the Asus BIOS flashback does not work on my board (for what reason ever).
So please make a note: When the flashback feature does not work, STOP.
I was not so wise and tried this guide "AMI Aptio UEFI using AFU". This guide is useless:
First the download link is wrong.
Second this guide is useless: All the points until 5a) make no sense, because cap file is protected and can't be loaded.
Then there comes 5b) "try AFU modified.rom /GAN command. /GAN is undocumented key meant ....."
There is no /GAN option on the latest Afudos.
I was then stupid, nothing damaged until this point, but I started trying other Afudos options....... Then I ordered via Ebay a new Bios, now the PC works again.

But of course, it was my fault, I should have FIRST gone through the postings of this thread .... Nevertheless I think it would be a good idea to take out the original HOWTO and put an actual guide. :)

Do you need help still flashing your modified BIOS, or did you get it all sorted out? You can removed your new BIOS and put aside, so you can get help flashing your original BIOS chip with the mod BIOS if you want to do that I can help.

I can also PM you several versions of AFU/AFUWin/AFUDOS that do have working /GAN function, but there is other ways around flashing the Modified Asus BIOS.
And since you only need the BIOS region flashed due to your mod specifics, you can use AFU/AFUWin with the /p switch only and it should go through find (BIOS/rom will need extracted from capsule first using UEFITool)

Hi, Lost_N_BIOS, thx for offering help.
I am not sure how to continue.
I don't want to override the new BIOS chip, but of course I still have the old Bios chip, would be nice to put the modified BIOS on it.
But doing a "hot flash", so removing the Bios after boot-up, is a bit risky, what do you think?
So I need a hardware programmier ....
I guess I killed my Bios chip, because I did not convert the cap file to a BIOS/rom file.