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Windows 7: AC'97 and HD audio front panel layouts

05 Dec 2009   #1

Windows 8.1 Pro RTM x64
AC'97 and HD audio front panel layouts

This shows the difference between the AC'97 and HD audio front panels.

AC'97 and HD audio front panel layouts-ac-97-dongle.png AC'97 and HD audio front panel layouts-hd-dongle.png

The main reason for the difference is to do with speaker assignment. With the older AC'97 system, only a single pair of stereo speakers was supported. These could be switched on and off by a standard switching stereo jack socket. With the introduction of HD audio, and the ability to feed upto 8 speakers (7.1 audio), a different method of muting had to be utilized. This method uses circuits built in to the audio chip itself to control the rear socket muting. All the front panel has to do is to provide the correct signals to the audio circuitry to tell it whether it should mute the rear panel or not. To do this, specially designed jack sockets are used. Inserting a set of headphones into the front panel socket will cause all rear panel sockets that have been assigned as speaker sockets to be muted. Since the rear microphone socket can also be re-assigned as a speaker socket, a similar arrangement also exists for a front panel microphone as well. This disables the rear pink (MIC) socket, but not if it is assigned as a speaker socket.
Note that an AC'97 style front panel WILL NOT mute speakers connected to the rear panel of a HD equiped motherboard - only a HD front panel is configured to do so.
Even cases that come with front panels fitted with both HD and AC'97 audio plugs for the motherboard will not mute these speakers as the jack sockets are still the type used for AC'97, meaning that the required muting signals are never received by the audio chip on the motherboard.

My System SpecsSystem Spec

24 Apr 2010   #2

win xp

Great info, just what I searched for.
My System SpecsSystem Spec
24 Apr 2010   #3

Windows 8.1 Pro RTM x64

You're welcome. It's just a pity that HD front panels are somewhat elusive and very difficult to find.
My System SpecsSystem Spec

24 Apr 2010   #4

Windows 7 Home Premium

Nice, thanks.... I've always wondered about the differences.

My System SpecsSystem Spec
24 Apr 2010   #5
Microsoft MVP

Win 7 Ultimate x64

Too take it a little further here is the difference in the pin outs for a the AC97 and HD Audio jumpers on a motherboard,

Also if you motherboard is like mine it will have a setting in the bios where you set it to either, depending on what is on the case.
My System SpecsSystem Spec
13 Mar 2011   #6

W7 Prof 64 bit

My Lian-Li A77 HD Audio plug is arranged like below.

1 black (gnd)
2 red (port1L)
3 black (presence)
4 brown (port1R)
5 orange (sense1 return)
6 yellow (port2R)
7 key
8 black (sense send)
9 green (sense2 return)
10 blue (port2L)

It looks like I have to swap the pins like this: (or I am nutz)
1 and 2
3 and 4
5 and 6
7 and 8
9 and 10

Note that the socket is on the Supreme FX mini card.
My System SpecsSystem Spec

 AC'97 and HD audio front panel layouts

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