From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MLHkL-00057k-4a for qemu-devel@nongnu.org; Mon, 29 Jun 2009 10:22:13 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MLHkG-000541-5T for qemu-devel@nongnu.org; Mon, 29 Jun 2009 10:22:12 -0400 Received: from [199.232.76.173] (port=58118 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MLHkG-00053r-0a for qemu-devel@nongnu.org; Mon, 29 Jun 2009 10:22:08 -0400 Received: from mx2.redhat.com ([66.187.237.31]:50574) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MLHkF-0001En-Is for qemu-devel@nongnu.org; Mon, 29 Jun 2009 10:22:07 -0400 Message-ID: <4A48CE67.9070705@redhat.com> Date: Mon, 29 Jun 2009 17:23:35 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] Implement PC port80 debug register. References: <1246262725-23825-1-git-send-email-jljusten@gmail.com> <4A48C5F5.6030402@codemonkey.ws> In-Reply-To: <4A48C5F5.6030402@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Jordan Justen , qemu-devel@nongnu.org On 06/29/2009 04:47 PM, Anthony Liguori wrote: > Jordan Justen wrote: >> From: jljusten >> >> 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