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Re: [OCLUG-Tech] A final BIOS question ??

William Case wrote:
> Hi;
> Is memory location FFFF0h, an
> address in the BIOS CMOS (in my system, the CMOS of the Intel Firmware
> Hub)? Or, is it a location in main system (RAM) (high memory)?  If so
> how does it get there?  If it is hardwired or embedded in some way, why
> is it considered part of system memory.  

The CPU knows that adress as part of its design.It may be in the
microcode of the Cpu or perhaps built into the hardware of teh CPU.
Intel or AMD can design it however it si convient to them.  The Mother
board will have eitehr some ROM in there, or may copy from rom to ram
beofore teh CPU is reset.  The memory map may get changed several times
in the POST process.  (why not you can't touch the Unit until the PSOT
finishes and it loods a boot sector for some device.

The engineers have choices about how they "make it so".  Once the Bios
starts it uses that address ot figure out where ots built in program is
to run, again the program may goive an I/O instuction that changes the
location of memory.  SOme systems even have the rom or the RAm (or both)
at more than one address - Easy if you jsut ignore some address lines -
Until they are ready to boogie.