pc bios read

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Hello,
    How do I read the bios flash on a pc? After the machine boots it looks
like the flash is overlaid with memory.

Steve





Re: pc bios read

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Write the program that uses only int13h, place it into the boot sector,
boot from the floppy.  The program should read the BIOS and write it's
contents to the floppy, block by block.  You don't need more than 50 bytes
of code to do this.

HTH,
   Vadim

Re: pc bios read
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Won't work. PC BIOSes are usually compressed miniature filesystems.
During boot, the BIOS is decompressed to shadow RAM and the physical
flash chip is swapped out. Once the system has booted, you can only
see the RAM copy, which is most definitely not a bootable copy of the
original data.

Re: pc bios read

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Well, you are most likely right.  The last time I've done something like
this was before flash was used in PCs.

   Vadim

Re: pc bios read
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The last time I *WANTED* to do this was when a PC BIOS consisted of 8K
of code. As a fun project, I disassembled an XT-clone motherboard BIOS
(one of those super-integrated "tiny turbo XT" boards barely big
enough to hold five slots, with everything except the CPU in one
208-pin QFP). The aim was to get sourcecode that would build with TASM
to a binary identical copy, and I didn't quite manage it because of
issues with different ways of expressing the same instruction in the
x86 opcode set.

Unfortunately, in more recent years I got dragged into needing to hack
buggy Advantech BIOSes and in the process I learned more than I ever
wanted to know about the anatomy of a modern BIOS.

Re: pc bios read

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With the same program offered by the vendor to reprogram it, usually.
If your vendor's flash update utility doesn't support this, this may
be reason to upgrade to a better vendor.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

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