http://www.cs.cmu.edu/~412/history/2006F/ac97

There's no source there, but you could probably find an email address at
http://www.cs.cmu.edu/~412 for someone who does have the source. It could be
on sources, though,  I haven't checked.
On Jan 17, 2011 8:36 AM, "Pavel Klinkovsky" <pavel.klinkovsky@gmail.com>
wrote:
>> There exist two different AC97 drivers; look at the port of Doom to plan9
>> for pointers to one of them.
> I have my IBM Think Pad with AC'97 running Plan9.
> The AC'97 driver supports only output mode.
> Any link to some different driver supporting also input mode?
>
> Pavel
>