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SubjectRe: [PATCH] Use correct x86 reboot vector
On Sun, 11 May 2003, Jamie Lokier wrote:

> Jos Hulzink wrote:
> > On Sunday 11 May 2003 05:50, Linus Torvalds wrote:
> > > Hmm.. Doesnt' a _real_ hardware reset actually use a magic segment that
> > > isn't even really true real mode? I have this memory that the reset value
> > > for a i386 has CS=0xf000, but the shadow base register actually contains
> > > 0xffff0000. In other words, the CPU actually starts up in "unreal" mode,
> > > and will fetch the first instruction from physical address 0xfffffff0.
> > >
> > > At least that was true on an original 386. It's something that could
> > > easily have changed since.
>
> I got my info from an article on the net which says that a 386 does
> behave as you say, but it is possible for the system designer to
> arrange that it boots into the 286-compatible vector at physical
> address 0x000ffff0. It states that the feature is specifically so
> that system designers don't have to create a "memory hole" (that's as
> much detail as it gives).

Guys, mem[0xfffffff0,...] == mem[0x000ffff0,...] since the hw remaps the
bios. Being picky about Intel specs, it should be f000:fff0 though.


- Davide

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