From: Avi Kivity <avi@redhat.com>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Jordan Justen <jljusten@gmail.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] Implement PC port80 debug register.
Date: Mon, 29 Jun 2009 17:23:35 +0300 [thread overview]
Message-ID: <4A48CE67.9070705@redhat.com> (raw)
In-Reply-To: <4A48C5F5.6030402@codemonkey.ws>
On 06/29/2009 04:47 PM, 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.
>
It's often used in BIOS code. There used to be seven-segment cards
you'd plug into a computer that would show you port 80 in real time. I
think it's a write-only port, though.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2009-06-29 14:22 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
2009-06-29 14:23 ` Avi Kivity [this message]
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
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