* William Case <billlinux [ at ] rogers [ dot ] com> [070908 11:27]:
> That's the $64,000 question. (Dating myself.)
Don't you mean $65,536 question?
> Even if the BIOS is shadowed into RAM, which is what happened on my old
> intel P4 and my new AMD 64 Athlon, RAM simply records an address for a
> ROM outside of the CPU and RAM. Where does the BIOS get those addresses
> and how does the CPU know how to interpret them? Are these addresses
> simply a fixed ISA-32 instruction? At the hardware level, a specific
> set of gates must be opened that lead to a bus?? that is the pathway to
> the ROM?
If you are asking about the "rest" of the BIOS, I think this is an
implementation specific detail. It could be stored at some higher 32bit
page, it could be fetched using something similar to the CMOS register
access.
You can have a look at...
http://www.jukie.net/~bart/blog/bios-disassembler
This let me follow the BIOS code from a machine I was doing some low
level hacking on.
-Bart
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