scott wrote:
>>> I believe what it *actually* does is yell "hey, somebody changed this!"
>>
>>  How does it do that? The bios cannot have sufficient info about the
>> graphics card in order to show a message on screen, especially if the
>> graphics card is currently in non-vga mode.
> 
> I would imagine it goes something like this:
> 
> Interrupt 13 handler (file I/O) code inside BIOS:
> 
> Check if trying to write to MBR (always on the same place)
> If not, write as usual to the drive, return
> Change screen mode to 720x480 (or whatever that one is the BIOS uses at 
> startup) using an interrupt 10 call

You can't call an interrupt from within an interrupt (at least, you 
couldn't when I was messing with them, but that was 12 years ago... of 
course, I doubt they've changed much since then).

-- 
...Ben Chambers
www.pacificwebguy.com

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