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Date: Wed, 3 Jan 1996 09:47:17 GMT
From: Steve Gailey <steveg@hplona90.uksr.hp.com>
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>   I have a few older (read: ancient!) Compaq systems I'd like to
>put FBSD on.  Unfortunately, Compaq (in their infinite wisdom -- NOT!)
>have fixed disk parameter tables in their BIOS.  So, regardless of
>the size of the (IDE) disk I might install, I am limited to
>whatever geometry Compaq has chosen to support.
>   I'd like to cut a new set of EPROMs with an altered disk table
>but the POST screams about bad checksums.  Anyone have a clue as
>to the algorithm employed and the location of the checksum image
>(before I start disassembling code)?

Just after the bios id AA55<size> is a checksum which is a checksum of all
the following bios. If you alter the bios, you must calculate a new checksum.

This is how the system ensures that the bios is not dammaged.

Steve Gailey
steveg@metrosol.demon.co.uk