Messages in this thread |  | | Date | Tue, 05 Dec 2000 16:15:05 -0800 | From | "H. Peter Anvin" <> | Subject | Re: That horrible hack from hell called A20 |
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Linus Torvalds wrote: > > So the "orb $2,%al ; andb $0xfe,%al" will potentially change both of > these. And I'd feel a hell of a lot more safe, if we avoided using 0x92 > except when we find that we absolutely _have_ to. > > How about making the keyboard controller timeouts shorter, and moving all > the 0x92 games to after the keyboard controller games. That, I feel, would > be the safest approach: try the really old approach first (that people are > the least likely to use as GPIO - it's just too damn painful to go through > the keyboard controller, and the keyboard controller A20 logic is just too > well documented, so nobody would use it for anything else). > > If the keyboard controller times out, or if A20 still doesn't seem to be > enabled, only _then_ would we do the 0x92 testing. > > Btw, do we actually know of any machine that really needs the "and $0xfe"? > That register really makes me nervous. >
Good question. The whole thing makes me nervous... in fact, perhaps we should really consider using the BIOS INT 15h interrupt to enter protected mode?
-hpa
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