Backup made using wrong awdflash.exe version is useless. In your case the backup file seems to be wrong. I used awdflash860C.exe for flashing BIOS on my ECS slot 1 motherboard and it was successful, but this version couldn't a produce backup that could be then flashed back. I got a 256kb file, but when trying to flash back the backup it complained about checksum error. I also have another backup made using an older awdflash and it is 128kb. However new BIOS files are 256kb. The correct version for my board is awd77.exe

You can try a few versions until it doesn't complain anymore. Don't use the force flag. In your case older than awd77.exe

so far i tried 625,625A,631,650D,707,764a all of them with no luck

below 6.6 I couldn't even backup the bios ... the awdflash764a made a correct backup with 128kb but then still the same "filesize error" ?!

it's weird because on the Gigabyte website the Bios comes bundled with the version 6.6

This kind of reminds me when attempting to flash the GA-586ATV motherboard with AWDFLASH and it worked with a very specific version (don't remember which one sadly).

Have you tried using UniFlash to see if everything works properly? Check if the BIOS chip and motherboard chipset is supported before using this program though.

Didn't know of the tool UniFlash. I tested it and it and did a backup but again it wrongly gave me 256kb? The new Bios would only be 128kb. Still not sure alltough my Flashchip + Chipset seems to be supported

There is also an option flashing without Bootblock what's that for?

Mmm, so it seems that it isn't supported.

The boot block is just a code that boots the computer with basic support in case something went wrong and you want to flash a working BIOS. Flashing without boot block is similar to the normal option, but it's more dangerous (can leave an incompatible boot block from a previous BIOS) and for that reason it is on the advanced menu.

You can read UNIFLASH.TXT file for more details about this.

This is where a TL866 comes in handy. Best $ spent on something thought would used only once or twice but it has more than paid for it self in terms of the hours saved over time.
Curious which Giga board you have ? Odd that you have a 2Mb bios chip but only flashing with a 1Mb (128K) bios. Probably why the saved files are 256K, tools are saving the entire BIOS contents which 1/2 is blank...

^ Exactly!
OEM variants and revisions can also be a cause of confusion...Gigabyte especially seems to have a lot of those mobo revisions. What are the exact model markings?
(hq pics welcome, as always!)

Maybe you could try checking the saved BIOS file contents with a hex editor, to see if it matches Horun's idea?
Perhaps the file size could be manually tweaked or forcing the write is possible some other way, but that just feels like a wrong way to go about it.
I find it very weird that the manufacturer's own tools wouldn't be able to handle their own files.

EDIT: wimsbios has both 128k and 256k variants listed with BIOS ID 2A69JG0FC-00, but there is no indication about the mobo revision.
But it's starting to look like those 128k versions are meant for mobo rev 1.0:
The manual for rev 2.x says the chip is 2Mb (as you've found out), however this one says 1Mb.
(The mobo revision isn't stated in that older one so I guess that means it's 1.0.)

mr.cat wrote on 2021-09-05, 23:48:

Gigabyte especially seems to have a lot of those mobo revisions. What are the exact model markings?

it's a GA - 686LX3 (rev. 2.0)

Some additional observations:

Gigabyte's taiwanese FTP site mirror at archive.org has a list of the BIOS versions, but none of the download links work.
However those files have been mirrored at mobokive and it seems all the LX3 ones are 128k!
Seems like an oversight on Gigabyte's part.
So wimsbios have probably dumped that 256k file themselves.

The sibling model 686LX4 has 256k and it's bundled with either AwdFlash 6.6 or "Flash Utility Ver.836", whatever that is.
So I don't think this 1Mb => 2Mb conversion is managed by their flashing tools (I could be wrong tho!)
The initial BIOS version (6lx4101.zip) for LX4 is actually 128k and they have a one-liner about it in their v1.03 update.

It seems the 256k version is rare (the wimsbios is the only one I spotted and it doesn't have direct dl), so could you post your dump here?
Maybe it can be patched if there's some particular problem you want to get solved.
(but it needs to be done by somebody more knowledgeable than me 🤣)

EDIT: OK it seems if you combine 128kB worth of zeroes followed by the 128k BIOS, the combined file will run in an emulator (with a mobo model that has 256k BIOS) 😁
Maybe some flash tools can do something like that on the fly (actually could be a bit risky to have that feature though).
The 256k versions on Gigabyte site ofc have actual content in that extra space, and not just zeroes.

1 - as said before, TL866 + an IC extractor is a must if one is tinkering with the bios. TL866 can write DIP32 EEPROMS directly, no adapters needed.

2 - why do you need to update the bios? You should update the bios only if the update solves a problem.

@mr.cat thanks gigabyte still have them listed too

https://www.gigabyte.com/Motherboard/GA-686LX … support-dl-bios

@mihai the TL866 is really the best option. I can try to flash it as many times there but again not that cheap device for a non heavy user

Id like to have the newest version of a Bios which I didn't have back in the day because of this stupid memory size error

Right, they do have a couple of the newest ones on the current site. Normally that's all you need but you know us retro-heads we prefer to conserve them all 😁
(Actually the US site gives me Bad Gateway, but they have mirror sites that work.)

Maybe that combination bios trick would work in a physical machine too, I mean I can't see why not?
That 128kB of zeroes is only needed so that the jump address is located in the right place.
But I must say I'm very hesitant to recommend trying that, unless there's some easy way to recover.

Getting a 256kB file when backing up a 2Mb/256kB EEPROM isn't a bug, it's a feature. Even if half of it is all zeroes, you get the full size as backup.

As for recovery - do you have another EEPROM? Preferably a 1Mb one? If so you could hot-flash here, so boot with the 2Mb EEPROM, then (while it's running) swap the chips around and flash the 1Mb ROM. No size mismatch, and if it goes wrong you can always put the working 2Mb EEPROM back.

Someone reccomend me to open the 128k file in a HexEditer and select all the contents and paste it to the end of the file, then save it it to 256k. Would that be a solution?

Is flashing via Motherboard even a good idea on precious old nostalgic Mobos?

Get a 2nd BIOS chip compatible with your board from a dead one (never throw dead boards straight away, remove at least the BIOS chip). Then you can do force flash on the new BIOS chip, swapping it just before you start flashing. Don't do force flash until then. You don't have to push BIOS chip all the way in, just slightly to make contact so that you can remove it with hand.

^ What he said 😁
It would probably work just the same. The contents of the first 128kB shouldn't really matter as long as it's exactly 128kB (131072 bytes). The actual BIOS payload must come last.
(And if you're unsure about the resulting file, you can give it a spin in an emulator as I did.)

EDIT: There seems to be a similar flash size mismatch going on in this thread, and the same conclusion:
ASUS SPAX hidden BIOS settings.

As for flashing classic boards, your call really...depends on what bugs will be fixed and if they really annoy you or not.
But it's not like you're permanently ruining if it your flash goes wrong. It'll just remain a brick until you come up with a recovery method...

Just to add my 2 cents.

I recall updating a gigabyte motherboard, with the latest bios available which had EFI support for the cdrom boot. (no GPT though)
the latest bios was double the size of the previous bios files available, probably due to the addition of the EFI part. and it was a hassle to actually update it.
I tried first with the dos updater that was available but that somehow didn't work, so ended up installing windows just to use the windows updater, which got the latest bios installed.

Enjoy !