From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: Jordan Justen <jljusten@gmail.com>
Subject: Re: [Qemu-devel] [PATCH] Implement PC port80 debug register.
Date: Mon, 29 Jun 2009 15:17:17 +0100 [thread overview]
Message-ID: <200906291517.18670.paul@codesourcery.com> (raw)
In-Reply-To: <4A48C5F5.6030402@codemonkey.ws>
On Monday 29 June 2009, Anthony Liguori wrote:
> Jordan Justen wrote:
> > From: jljusten <jljusten@jljusten-laptop.(none)>
> >
> > In PC systems, the byte I/O port 0x80 is commonly made into a
> > read/write byte. BIOS and/or system software will often use
> > it as a simple checkpoint marker.
>
> What software does this? Typically, port80 is used as an IO delay
> mechanism. I'm not aware of it being used to read/write arbitrary data.
Port 0x80 is generally the bios debug port. It's not uncommon for motherboards
to display the values written to this port via an onboard 7-segment LED.
Paul
next prev parent reply other threads:[~2009-06-29 14:17 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-29 8:05 [Qemu-devel] [PATCH] Implement PC port80 debug register Jordan Justen
2009-06-29 13:47 ` Anthony Liguori
2009-06-29 14:17 ` Paul Brook [this message]
2009-06-29 14:23 ` Avi Kivity
2009-06-29 14:34 ` Chris Lalancette
2009-06-29 15:26 ` Jordan Justen
2009-06-29 15:31 ` Anthony Liguori
2009-06-29 16:07 ` Jordan Justen
2009-06-29 17:11 ` Avi Kivity
2009-06-29 18:39 ` Anthony Liguori
2009-06-29 18:43 ` Avi Kivity
2009-06-29 18:46 ` Alexander Graf
2009-06-29 18:57 ` Avi Kivity
2009-06-29 19:00 ` Jordan Justen
2009-06-29 19:02 ` Jordan Justen
2009-07-01 7:39 ` Jordan Justen
2009-07-09 18:58 ` Anthony Liguori
2009-06-29 15:36 ` Avi Kivity
2009-06-29 21:53 ` Jamie Lokier
2009-06-29 23:18 ` Carl-Daniel Hailfinger
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=200906291517.18670.paul@codesourcery.com \
--to=paul@codesourcery.com \
--cc=jljusten@gmail.com \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.