we are trying to do a rather off-the-wall thing. the big picture: we have classified data that we want to encrypt on all writable partitions on our hard drive(s). we need to store the encryption/decryption "keys" - two redundant 32 byte entries - for this data external to these drives. one place we thought of was in bios. these keys will be used for every read/write from/to the hard drives, so we would like them be be accessible in the lower part of ram like all other bios data (if possible). the keys may need to be changed sometimes at boot-up by an application and not by entering the standard bios menus. is this possible?
IIRC BIOS level memory is all reserved and mapped. Not sure there is room for anything else. Not really sure how to "extend" BIOS memory reservation. Have you considered a small SSD drive? The controller would have it's own BIOS outside of the system BIOS, which you might be able to work with.
I'm by no means an expert, but messing with the BIOS chip is a distinctly dangerous idea. The potential to brick your system is very high if you ever actually manage to do it. Have you considered some sort of encryption key on a flash drive like Thanatos said? I'm sure that there is actually some sort of PCI device made specifically for this purpose as well.