Can you find the Micron board # ? Should be on a little sticker and according to Micron archive it could be MBD001109-xx or MBD001138-xx.
Does your board have Yamaha sound chip, no sound chip or Crystal sound chip ?
Might want to read this topic: Micron Millennia in a full tower case
PC Hoarder Patrol attached the Micron bios ...Re: Micron Millennia in a full tower case

BitsUndBolts wrote on 2024-09-28, 04:55:

The board seems to have been distributed by "Micron Electronics" (I do not believe there is a relation to the memory manufacturer).

Micron Electronics was part of the same company that now makes mostly memory.

Post a pic of the motherboard as if it has the included yamaha sound chips it uses a different bios.

I have a one of these boards and have only updated it with Micron bios and not the stock Intel ones. Horun has linked PC Hoarder Patrol's post that has the correct info.

I mean the Intel Bios should work but I used the Micron one.

The Micron P15 listed earlier might be the newest you can flash without an error, has to due with that Invalid string in header (think it has to be 05a as PC Hoarder said)..
Here is the Micron P12-0013 for SE440BX-2 in case you want to try it. From the internal text "Thank you for choosing micronpc.com. A blank 3.5" floppy is needed before proceeding.... "
And the Update text...

Horun wrote on 2024-09-28, 14:12:

Can you find the Micron board # ? Should be on a little sticker and according to Micron archive it could be MBD001109-xx or MBD0 […]
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Can you find the Micron board # ? Should be on a little sticker and according to Micron archive it could be MBD001109-xx or MBD001138-xx.
Does your board have Yamaha sound chip, no sound chip or Crystal sound chip ?
Might want to read this topic: Micron Millennia in a full tower case
PC Hoarder Patrol attached the Micron bios ...Re: Micron Millennia in a full tower case

Thank you all for the quick response! This is exactly what solved my issue.
I tried both BIOSes (P12 and P15 from the link / PC Hoarder Patrol) - they work perfectly on the board.
I am a bit surprised that those BIOSes aren't on The Retro Web.
I will submit them just in case someone else is looking for them as well.

My board does have the Yamaha Sound chip and has the model number: AA 719944-213

The issues seems to be the identifier (header) in the BIOS file:
86A = INTEL
05A = MICRON

Although I did not test BIOS P12 (4S4EB2X0.05A.0013.P12) thoroughly, it did POST and seems to work.
I am using P15 (4S4EB2X0.05A.0016.P15) from the link shared above - which did solve an issue with Wake-On-LAN (WOL).

Thanks again for everyone's help!

I have quite a few different OEM boards and it is best to use the OEMs Bios over Intels in most cases.

It is always best to check the OEM identifier in the bios string.

https://dosdays.co.uk/topics/mobo_ident.php#Phoenix

Glad it worked.