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Date: Wed, 06 Dec 2000 10:26:46 -0800
From: "H. Peter Anvin" <hpa@transmeta.com>
Organization: Transmeta Corporation
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To: root@chaos.analogic.com
CC: Linus Torvalds <torvalds@transmeta.com>,
        Kai Germaschewski <kai@thphy.uni-duesseldorf.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: That horrible hack from hell called A20
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"Richard B. Johnson" wrote:
> 
> The protected-mode switch in INT 15 is probably the least tested BIOS
> function ever. I wouldn't trust it, and relying on it will put further
> burden on embedded Linux developers, many of whom don't even have a
> BIOS. It is 'least tested' because there is no way provided to get
> back to real-mode. This implies that somebody probably 'tested' it
> once, verified that some simple 32-bit function executed for a
> few microseconds, then declared; "It works!".
> 

And of course, that's pretty much all we'd trust it to do.  Personally,
I'd rather try to use the A20 gate function, if it works.  I suspect that
between the machines where the BIOS or the KBC works, we should be close
to 100% coverage.

-- 
<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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