Re: setup.S: A20 enable sequence (once again)

From: H. Peter Anvin (hpa@zytor.com)
Date: Mon Nov 06 2000 - 17:06:04 EST


Followup to: <E13stqG-0006eJ-00@the-village.bc.nu>
By author: Alan Cox <alan@lxorguk.ukuu.org.uk>
In newsgroup: linux.dev.kernel
>
> > This doesn't really work. Neither the fast A20 gate nor the KBC is
> > guaranteed to have immediate effect (on most systems they won't.)
>
> Fast A20 gate happens to be immediate on all the embedded kit I know so its
> probably acceptable, and if its too slow it still does the kbc timeout. Since
> its generally on chip they dont muck about talking to keyboard and other junk
> I/O controllers.
>

I'd rather do it "right", which is to poll for A20 in the same loop as
we wait for the KBC to become available.

        -hpa

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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