x86 programming question

Chris Johns cjohns at cybertec.com.au
Fri Aug 24 19:23:28 UTC 2001

Joel Sherrill wrote:
> I know the interrupt and know how to write the code in real mode to do
> this call.  However,
> the results of this call are of more use in protected mode.  So I saw
> only a handful of options:
>   + figure out how to do the BIOS call in protected mode
>   + do the BIOS call in real mode and figure out how to save the results
>       in memory in such a way that they can be retrieved in protected mode.
>   + (from Rosimildo) leave the memory size in a register at the time of
>      transition from real to protected mode then save it away for later use.
> So ideally I would like a generic way to perform a BIOS call from protected
> mode.

I suggest you look into the Etherboot project code on SourceForge :


Look in start32.S in the src directory. Near the end is call to switch
between protected and real mode. Maybe they will help.

 Chris Johns, cjohns @ cybertec.com.au

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