Messages in this thread | | | Subject | Re: [PATCH] Use correct x86 reboot vector | From | (Eric W. Biederman) | Date | 11 May 2003 11:54:20 -0600 |
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Linus Torvalds <torvalds@transmeta.com> writes:
> On Sat, 10 May 2003, Jamie Lokier wrote: > > Jos Hulzink wrote: > > > For the sake of bad behaving BIOSes however, I'd vote for the f000:fff0 > > > vector, unless someone can hand me a paper that says it is wrong. > > > > I agree, for the simple reason that it is what the chip does on a > > hardware reset signal. > > 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.
Correct. And no one has changed it since. I use that all of the time.
> In other words, you're all wrong. Nyaah, nyaah.
However 0xf000:fff0 is as close as you can get, and since that is usually RAM it can do something different on a reset vs a reboot if it wants to.
Using 0xf000 is just polite as it allows relative jumps.
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