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Bug#606482: no headphone output on ASUS M4A785T-D motherboard



* Ben Hutchings [2012-02-27 14:50:45 +0000]:
> On Mon, 2012-02-27 at 09:06 +0100, Sergio Gelato wrote:
> > * Jonathan Nieder [2012-02-25 21:19:43 -0600]:
> > > Sergio Gelato wrote:
> > > 
> > > > The problem turned out to be due to an inappropriate BIOS configuration
> > > > setting. The "Front Panel Select" setting needed (for my specific case)
> > > > to be set to "AC97" instead of "HD Audio". Found thanks to some comments in
> > > > https://bugtrack.alsa-project.org/alsa-bug/view.php?id=5309
> > > > (especially note 23449).
> > > >
> > > > No kernel changes needed.
> > > 
> > > That sounds like a workaround rather than a fix.
> > 
> > I don't see it that way: my front panel is in fact of the older AC97 type,
> > so the earlier BIOS setting was incorrect and changing it was the proper
> > thing to do.
> > 
> > When I installed this motherboard I wasn't sure whether I had HDA or AC97,
> > so I decided to try one setting and see if it worked. The fact that the
> > Ubuntu 10.04 kernel appeared to work even with the setting I tried first
> > actually made it harder for me to correctly diagnose the problem.
> 
> AC97 and HDA are specifications for the interface from the PCI(e) bus to
> the sound chip.  Some chips support both interfaces, either at the same
> time or selected by firmware (BIOS setting).
> 
> [...]
> > My preferred approach would be to add this to the troubleshooting guides:
> > if your audio front panel is misbehaving, check that it is of the right type
> > for your motherboard. (Probably with some additional words about AC97 vs.
> > HDA and/or a link to an external reference.)
> [...]
> 
> The connection from the sound chip to any external connectors is
> independent of such specifications; there is no such thing as an 'HDA
> front panel'.  However the two specifications have different ways for
> the chip/board to describe which connectors are wired to it.  The
> problem you're seeing is very likely related to some oddity of the
> description.

If you say so. I don't claim any real expertise in this area. I do note that
http://www.intel.com/support/motherboards/desktop/sb/cs-020642.htm#standards
says in part:
	"To identify your front panel audio solution’s audio codec, refer 
	 to the specifications or documentation for your PC chassis or 
	 front panel module. Note that AC’97 and HD Audio front panel 
	 solutions are different and may not be directly compatible 
	 or interchangeable."
and goes on to point out a physical wiring difference involving pin 4.



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