AC'97 (short for Audio Codec '97 ) is an audio standard, which was developed by the Intel Architecture Labs in 1997 and is mainly used by on-board chips for motherboards, rare modems and sound cards.


Chipsets with integrated audio components contain two, three optional components:

  • AC'97 digital controller that is coupled to the PCI bus in the I / O Controller Hub (ICH) of the chipset and controls its own bus, AC-Link, the external AC'97 codec analog module, and optionally a proprietary ended CNR or AMR card ( audio and modem Riser ).
  • AC'97 analog codec, which integrates the mixer and the analog ( PCM ) digital to analog converter (DAC) and the analog -to-digital converter (ADC).
  • OEM riser slot & card: AMR or CNR.

The standard defines an audio architecture for the PC, which was built by different manufacturers for different chipsets as low-cost minimum equipment with multimedia capabilities. Pin contact strips on motherboards for coupling of front panel ( FP_AUDIO ), which are designed, in contrast to the connectors on the AC'97 -2 .3 -compliant motherboard, not for Jack Sensing, are reported as a legacy AC'97. Pin contact strips that are designed for Jack Sensing accordance with AC'97 Rev. 2.3 are referred to as HD audio. Jack Sensing requires a different construction electromechanical jacks where the plug does not disconnect the idle contact, but includes an insulated switch. (In short: HD Audio ) From 2004 the AC'97 standard of Intel's High Definition Audio interface has been replaced.


  • AC'97 1.x compliant: sampling rate fixed 48 kHz, 16-bit full-duplex audio codec (DAC, ADC ), microphone input ( MIC1 ) with 20dB preamplifier and power supply ( with a maximum of 5 mA load) for electret microphones ( MIC_BIAS ), mono - output ( MONO_OUT ) for telephone or internal speaker ( SPKR ), stereo output ( LINE_OUT ), proprietary modem support ( LINE1 I / O, GPIO ), no optional extensions ( 2.1: extended audio, extended modem feature set; 2.2: enhanced riser audio, 2.3: extended configuration information).
  • AC'97 2.1 compliant: optional variable sampling rate ( rate conversion can be done in software by the driver in hardware 48 kHz and 44.1 kHz, optionally doubled to 88.2 kHz or 96 kHz ), optional 18 - or 20 -bit codec resolution (not for Phone), multi-channel sound (second stereo output ( AUX_OUT ), configurable as a second output or optionally as 4 or 6 -channel output ( LINE_OUT 4CH_OUT AUX_OUT, ​​with optional 3D stereo expansion ) ) option a third stereo input channel, standardized modem support.
  • AC'97 2.2 compliant: enhanced support for AMR Cards: optional support for second telephone line ( LINE2 I / O, HSET I / O); optional S / PDIF for 5.1 Dolby Digital audio (AC -3) - however, there are several reasons why this equipment feature works only as appreciation of the list of features.
  • AC'97 2.3 compliant: optional Jack Sensing informed that using appropriate connectors on the driver presence and type { passive boxes, headphones, amplifiers, microphone } of a connected socket on the device and thus allows a suitable automatic configuration of each port (audio plug-and- Play).

Not all existing on-chip standard -compliant connections are always available to everyone as a standards-compliant board marked as terminals. The AC'97 standard does not dictate how any sockets would perform. A version of the jacks than 3.5 mm jack is implicit in Intel Front Panel I / O Connectivity Design Guide.

Microphone Connection problem

A AC'97 microphone port provides supply voltage ( MIC_BIAS ) on the center contact. If a mono plug ( two pin) plugged in, the power supply voltage is pulled to ground. To electrical damage must not result in the short-circuit if the condition set to " no front panel connected " corresponds.

A mono Electret mono plug Tonaderspeisung expected at the plug tip. The plug 's tip supplies AC'97 but only with supply voltage when stereo microphones are supported. Electret microphones require the supply voltage. Dynamic microphones, however, may not be applied to the supply voltage.

AC'97 audio connection

Plug contact

The AC'97 audio plug contact is designed as ten -pin plug connector in not necessarily always the very same pinout.

If no front panel is connected, contacts must be bridged.

Connection cable

The connection cable is 45 cm long ( 17.75 " / -0.25 " ) and four individually shielded with braided, twisted AWG 26 twisted pairs exist ( conductor cross section 0.14 mm ²) with a common shield consists of braid and foil (SF / STP cable).

The double wires form:

To avoid ground loop, the shield must not be placed on AUD_GND even if a second AUD_GND pin is provided. They must be connected solely to the side of the front panel to the housing.