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Date: Thu, 14 Mar 2002 13:24:19 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: John Heil <kerndev@sc-software.com>
cc: <linux-kernel@vger.kernel.org>,
        Martin Wilck <Martin.Wilck@fujitsu-siemens.com>
Subject: Re: IO delay, port 0x80, and BIOS POST codes
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On Thu, 14 Mar 2002, John Heil wrote:
> 
> No, the better/correct port is 0xED which removes the conflict.

Port ED is fine for a BIOS, which (by definition) knows what the
motherboard devices are, and thus knows that ED cannot be used by
anything.

But it _is_ an unused port, and that's exactly the kind of thing that
might be used sometime in the future. Remember the port 22/23 brouhaha
with Cyrix using it for their stuff, and later Intel getting into the fray
too?

So the fact that ED works doesn't mean that _stays_ working.

The fact that 80 is the post code register means that it is fairly likely 
to _stay_ that way, without any ugly surprises.

Now, if there is something _else_ than just the fact that it is unused
that makes ED a good choice in the future too, that might be worth looking
into (like NT using it for the same purpose as Linux does port 80),

		Linus

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