Re: [Qemu-devel] [PATCH] Implement PC port80 debug register.

[Avi Kivity]

On 06/29/2009 04:47 PM, Anthony Liguori wrote:
> Jordan Justen wrote:
> > From: jljusten <address@hidden(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