small changes in BIOS from identical MBs \ VOGONS

small changes in BIOS from identical MBs

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First post, by tony359

tony359 Offline

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Hi all

I am curious about something. I've been working on some Asus P5P800-VM boards and as a "restoration" process I always read and write the BIOS back on the chip, to prevent bit rotting.

Those boards have all the same BIOS version but I've discovered there is always a small difference between them. Always in the same place.

Given the boards are the same model and revision and the BIOS is the same version, what could possibly be that difference?

Attached a screenshot of the different bits.

Thanks!

My Youtube channel: https://www.youtube.com/@tony359

Reply 1 of 5, by MagefromAntares

Posted on Today, 10:33

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Hi,

As these bytes are near the string "System Serial Number", I think it is logical to assume that one of them is the serial number, there is also a "System Version" string nearby, so the another one might be an internal version number which might differ from the BIOS version number.

If I had to guess the serial number is the larger block and the version the smaller one.

Obviously this is only conjecture on my part, but it seems logical for these values to be near their description strings.

Reply 2 of 5, by tony359

Posted on Today, 10:51

tony359 Offline

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Interesting I didn’t know the bios contained custom data. But that means that if I flash the bios with a programmer I lose that data? I’ll se if there is a valid SN in that bios.

My Youtube channel: https://www.youtube.com/@tony359

Reply 3 of 5, by MagefromAntares

Posted on Today, 10:58

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The serial number is there so they can track if a board gets sent back with an error to know which manufacturing line it was produced. It is encoded into the ROM because then it cannot be as easily tampered with as written text on the board.

Reply 4 of 5, by aVd

Posted on Today, 11:25

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Hi, Tony.
I'm not 100% sure, but those little differences could be due to different data stored in DMI tables.

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Reply 5 of 5, by MagefromAntares

Posted on 11 minutes ago

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aVd wrote on Today, 11:25:
I'm not 100% sure, but those little differences could be due to different data stored in DMI tables.

That is a definite possibility, DMI tables can contain different information, including a serial number. If tony359 uses Linux a utility named dmidecode is most likely available in the distributions package repository and the data can be checked to match.

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