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I'm currently setting up a older system in a new case (i'll be upgrading it in stages, and the old parts then go back into the old case ;p), and i'm having a bit of confusion over which cable to use, and what the difference is.

The cable looks somewhat like this enter image description here, with the AC 97 connector attached to the HD audio connector. They both appear to have the same kind of connector (right down to the 'key' - the space where there's no pin and its filled up), apparently the same colour codes at close inspection and so on.

What's the difference between these cables, and when do i know what to use? In my case the sound chip is a ALC888 but i'm more interested in a generic, all purpose answer, rather than one specific to this. The header on the system itself is marked 'Audio'.

If more specific information is needed, i've put the motherboard from a dell 530 into a cosair graphite 600T, just to test the case pending the rest of my hardware.

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up vote 23 down vote accepted

The correct one to use depends on your case. Those cables are typically used to connect front panel headphone/microphone ports. While the connectors may look identical, the pinouts are different and not really interchangeable. The matching connector on your case should be labelled accordingly, I know mine is labelled HD Audio.

HD Audio is intended to replace AC'97. HD Audio is generally more capable. The linked articles have more detail on that. For average home use, there shouldn't really be a noticeable difference.

The rest of this answer will be referencing the Intel Front Panel I/O Connectivity Design Guide, page 19. They also have schemantics on pages 20 and 25 if you care. I will be adding emphasis.

Front panel audio design in conjunction with motherboard audio header design is dependant upon the type of audio CODEC being used on the motherboard. In the past, AC’97 Integrated Audio CODECs were prevalent. With the introduction of Intel High Definition Audio, many new motherboard designs are switching over to High Definition (HD) audio CODECs. Designers should note that AC’97 and Intel High Definition Audio front panel motherboards and I/O cards implementations are different and may not be directly compatible or interchangeable

Some sources indicate that it is/may be necessary to switch audio output modes in the BIOS configuration or with a jumper. It is recommended that you look at your motherboard manual. My own motherboard (MSI P67A-C45) manual just says it's compliant with the Intel Front Panel I/O Connectivity Design Guide, not all that much information. Dell manuals describe it as front audio (F_AUDIO) and don't indicate any such jumper, and only describe the BIOS option Onboard Audio Controller as Enabled or Disabled (Enabled by default).

Passive AC’97 analog front panel dongles (ones which leave the 5V Analog pin-7 line unconnected on the dongle) may be used with the Intel® HD Audio analog front panel header. But note that the front panel jack detection and re-tasking functionality will be lost as the AC’97 jacks cannot support connection to the SENSE line. In addition, software must be aware that an AC’97 dongle is being used with an Intel® HD Audio analog header since the software might need to dedicate codec ports that are connected to the header to meet the product’s intended functionality.

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The header on mine is just labelled audio. On the other hand, the manual (which i SHOULD have looked up first) refers to it as a HDA header. This answers my question though, and gives me an idea what works. – Journeyman Geek May 1 '12 at 8:33
Just to note, there's a third kind of connector i came across, labelled azalia - which is a bundle of loose connectors. This apparently seems to be for systems with non standard HD audio implimentations. Adding this as a comment in case someone comes across it. – Journeyman Geek May 22 '12 at 3:36
To add more info, looks like AC97 is not supported by OSX, so you won't be able to have front panel audio in a Hackintosh unless you use HD Audio. – Lucio Paiva Oct 10 '14 at 2:48

I'm not sure of the exact different (I assume that HD audio will gives better audio quality) but I'll always go for HD audio if the mainboard has it, if the mainboard only has AC97 then I'll use AC97 connector.

BTW, the HD audio connector can be used with AC97 as well. Incase your case only has HD connector but your board only has AC97

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AC97 cables usually have an empty socket in pin location 4. On the other hand HD audio cables have a wire and terminal connecttor lurking there, waiting silently in that cold dark hole poised and ready for the time when a naive unsuspecting pin 4 (who isn't even old enough to leave his motherboard) slips into the High Definition Audio clutches of that extra wire.. .

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