From: "H. Peter Anvin" <hpa@zytor.com>
To: linux-kernel@vger.kernel.org
Subject: Re: IO delay, port 0x80, and BIOS POST codes
Date: 14 Mar 2002 13:56:20 -0800 [thread overview]
Message-ID: <a6r6a4$8hg$1@cesium.transmeta.com> (raw)
In-Reply-To: <Pine.LNX.4.33.0203141324480.9855-100000@penguin.transmeta.com> <Pine.LNX.3.95.1020314164142.382B-100000@chaos.analogic.com>
Followup to: <Pine.LNX.3.95.1020314164142.382B-100000@chaos.analogic.com>
By author: "Richard B. Johnson" <root@chaos.analogic.com>
In newsgroup: linux.dev.kernel
>
> Well no, IO doesn't "time-out". The PC/AT/ISA bus is asychronous, it's
> not clocked. If there's no hardware activity as a result of the write
> to nowhere, it's just a no-op. The CPU isn't slowed down at all. It's
> just some bits that got flung out on the bus with no feed-back at all.
>
An OUT on the x86 architecture is synchronous... the CPU will not
proceed until the OUT is present on the bus. This is a requirement of
the SMM architecture, actually.
-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 <amsp@zytor.com>
next prev parent reply other threads:[~2002-03-14 21:57 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-03-14 17:11 IO delay, port 0x80, and BIOS POST codes Martin Wilck
2002-03-14 17:54 ` Richard B. Johnson
2002-03-14 18:10 ` Alan Cox
2002-03-14 19:23 ` Linus Torvalds
2002-03-14 19:46 ` H. Peter Anvin
2002-03-14 20:43 ` John Heil
2002-03-14 21:03 ` Richard B. Johnson
2002-03-14 21:19 ` Pedro M. Rodrigues
2002-03-14 21:26 ` John Heil
2002-03-14 21:41 ` Richard B. Johnson
2002-03-14 21:26 ` Linus Torvalds
2002-03-14 21:44 ` Richard B. Johnson
2002-03-14 21:56 ` H. Peter Anvin [this message]
2002-03-14 22:11 ` Richard B. Johnson
2002-03-14 22:20 ` H. Peter Anvin
2002-03-14 22:25 ` Richard B. Johnson
2002-03-14 22:58 ` Alan Cox
2002-03-14 22:56 ` Alan Cox
2002-03-14 21:11 ` H. Peter Anvin
2002-03-14 21:24 ` Linus Torvalds
2002-03-14 21:57 ` H. Peter Anvin
2002-03-14 22:06 ` John Heil
2002-03-14 22:55 ` Alan Cox
2002-03-14 22:39 ` John Heil
2002-03-14 23:29 ` Alan Cox
2002-03-15 0:12 ` David Golden
2002-03-15 0:11 ` John Heil
2002-03-19 14:25 ` Pavel Machek
2002-03-15 11:30 ` Eric W. Biederman
-- strict thread matches above, loose matches on Subject: below --
2002-03-14 18:18 Thunder from the hill
2002-03-15 11:46 ` Martin Wilck
[not found] <3C90E983.5AC769B8@ngforever.de.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.33.0203151243430.1477-100000@biker.pdb.fsc.net.suse.lists.linux.kernel>
2002-03-15 11:51 ` Andi Kleen
2002-03-15 12:47 ` Martin Wilck
2002-03-15 12:52 ` Andi Kleen
2002-03-15 15:07 Thunder from the hill
2002-03-15 17:39 Gerald Champagne
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