UEFI Bios modding on Linx 12V64 (AMI Aptio V) HELP

Hi there, super new to bios modding and diving into the rabbit hole somewhat unintentionally!

Backstory… I’ve got an old Linx 12V64 Tablet (Linx 12V64) that I wanted to revive and put to use. during my internet travels on how to change boot logos (Initially the Windows boot logo) I came across information on ChangeLogo Tool 5 for AMI Bioses. From attempting to dump the bios using the AMI tools, I discovered/believe I have an Aptio V UEFI Bios. Thinking I was being careful, I use the AFUWIN flasher to DUMP the bios. Opened it in changelogo tool, changed the logo, saved it, rebooted into EFI Shell, and used AMUEFI Flasher to flash my modified rom using “amuefix64.efi myrom.rom /GAN” (First attempt gave me a " 18 - Error: Secure Flash Rom Verify fail" to which I discovered I apparently needed a flasher version that supported GAN). I was unable to boot FreeDOS so couldn’t use DOS to flash hence using the EFI Shell. I obv did something wrong as It resulted in a paper weight! A whole day of researching and pulling the tablet apart I Identified I have a WINBOND W25Q64FWIG. Bios dump Should have been 8MB I believe, but mine had dumped only 4MB. I’m assuming I needed a /P option or something that I didn’t use and so screwed up big time. Some more research and I came across the CH341A Flasher (And it’s required volt mod depending on model) - and knew my Winbond chip was 1.8v from the datasheet. Next problem, was that the company literally don’t support anything anymore. No spare parts (that’s a whole different story) and other than a Win10 Driver Package or Full OS Image, they don’t have any BIOS downloads. I emailed them to be basically told “We don’t offer support anymore, goodbye”. More searching for what felt like days, and as far as I can tell there’s NO BIOS available for my 12V64 on the internet. I did however come across a single random post that had a 12X64 BIOS. Since the 2 were produced around the same time, and 99% same hardware, I figured “well, it’s already dead anyways, so I can’t make it worse” and flashed the 8MB 12X64 Bios via the CH341A Flasher. SUCCESS My paperweight finally came to life again! I was able to boot the tablet, and enter the BIOS and set all my BIOS settings as required and boot into my Windows installation again. Hurrah. But now my bios reports it’s a “12X64” when it’s a “12V64”. I thought to myself, OK, I have this CH341A flasher that will dump the entire 8MB ROM. Let’s dump it again, and mod it again since I now know I can revive it. I used AMI BCP to change strings and ChangeLogo again. I flashed the new rom, and boom - paperweight again. I re-flashed the 8MB DUMP I had just taken prior to modding, and it revived it again. So this time I decided I would ONLY change the bios strings to match 12V64 instead of 12X64. Flashed the string modded UEFI BIOS, and boom, another paperweight, again! So I re-flashed the dump, and it came alive again.

I’m on the spectrum, thus it creates an inherent need to know and figure this out…

So, a few questions: 1) What am I doing wrong? Why can’t I even change a BIOS string without creating a paperweight? 2) I’m using AMI BCP 5 to edit strings and the resulting rom is 8MB as expected - should I be using different tools? 3) Is there some kind of CRC check? or Signature Verification I’m missing? 4) Is this “normal” when it comes to bios modding?

I’ve attached 2 rom file incase anyone wants to inspect them. “Original.rom” is my 8MB DUMP that works, “Updated Strings.rom” is one I modded the BIOS Strings using AMI BCP Tool and does NOT Work.

As a new user I apparently can’t upload files to my post, so I have uploaded the BIOS ROMs here: https://mega.nz/folder/gfJ3ETBL#AtSg7iowxEv9qM_hNlppMw

AMItools (Even as said for Aptio V) around the web breaks the signature/security/integrity of the bios image.
These tools were successful in Aptio IV…now very, very few Aptio V bios can be touched with it without breaking as you saw…the most modern the worst.
These mods have to be done by hexedit, guid replacing/edit etc…not an easy task on some bioses.
Dont ask how to do yours, good luck.

EDIT: Other method to try, dumping only bios region with Intel FPT tool… if possible, requires regions access read/write, now same edit tryouts on this image and flash again with fpt.
Do pay attention to the type/proprieties of image of the logo

I’m guessing there’s no easy way to disable UEFI Signature requirement / verification etc?
I replaced the logo via GUID and it still refuses to boot. I obv verified the rom was valid and complete but it still didn’t like it - even hex editing strings refuses to boot. Literally any change no matter how small breaks it :frowning: