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{{short description|Audio codec}}
{{more citations needed|date=December 2019}}

'''AC'97''' (''Audio Codec '97;'' also '''MC'97''' for ''Modem Codec '97'') is an [[Sound reproduction|audio]] [[codec]] standard developed by [[Intel Architecture Labs]] and various codec manufacturers in 1997. The standard was used in [[motherboard]]s, [[modem]]s, and [[sound card]]s.

The specification covers two types of components, and the '''AC-Link''' digital interface between them:
# an AC'97 ''digital controller'' (DC97), which is typically built into the [[Southbridge (computing)|southbridge]] of the [[chipset]], and
# an AC'97 audio and/or modem ''codec'', available from several vendors, which contains the analog components of the architecture.

AC'97 defines a high-quality, 16- or 24-[[bit]] audio architecture with [[5.1 surround sound]] support for the PC. AC'97 supports a 96&nbsp;kHz [[sampling rate]] at 24-bit stereo [[Audio bit depth|resolution]] and a 48&nbsp;kHz sampling rate at 24-bit stereo resolution for multichannel recording and playback.

Integrated audio is implemented with the AC'97 Codec on the [[motherboard]], a [[communications and networking riser]] card, or an [[audio/modem riser]] card.

The first shipping system was in the [[Cyrix]] [[MediaGX]], in 1997. Intel started shipping the initial [[I/O Controller Hub]] support in 1999, and it wasn't until public shaming<ref>{{Cite news |last=Thomas |first=Andrew |date=September 7, 2000 |title=Intel not shipping the best drivers for its Easton mobo |work=The Register |url=https://www.theregister.com/2000/09/07/intel_not_shipping_the_best/}}</ref> in 2000, that most PC OEMs started shipping AC'97 audio as the default.

In 2004, Intel released [[Intel High Definition Audio]] (HD Audio) which is a successor that is not [[backward compatibility|backward compatible]] with AC'97.<ref>{{Citation|publisher=Intel Corporation|year=2010|chapter-url=http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/high-definition-audio-specification.pdf|title=High Definition Audio Specification|version=Revision 1.0a|page=17|chapter=1.2.1 AC'97 Compatibility}}</ref> HD Audio has the capability to define up to 15 output channels, but in practice most motherboards provide no more than 8 channels ([[7.1 surround sound]]).

== Revisions ==
{{missing information|section|revision dates (which year)|date=August 2022}}
AC'97 has had several revisions:<ref name="ac97">{{citation |archive-url=https://web.archive.org/web/20090824055417/http://download.intel.com/support/motherboards/desktop/sb/ac97_r23.pdf |archive-date=August 24, 2009 |url=http://download.intel.com/support/motherboards/desktop/sb/ac97_r23.pdf |title=Audio Codec '97 |version=Revision 2.3 Rev 1.0 |publisher=Intel Corporation |date=April 2002 |access-date=December 22, 2007 |url-status=bot: unknown }}</ref>

* AC'97 1.x compliant indicates fixed 48&nbsp;kHz sampling rate operation (non-extended feature set)
* AC'97 2.1 compliant indicates extended audio feature set (optional variable rate, multichannel, etc.)
* AC'97 2.2 compliant indicates extended audio, enhanced riser audio support, and optional [[S/PDIF|Sony/Philips Digital Interface Format]]
* AC'97 2.3 compliant indicates extended configuration information and optional [[jack sensing]] support

AC'97 revision 2.3 enables [[Plug and Play]] for the end user. This revision provides means for the audio codec to supply parametric data about its [[analog device|analog interface]] much like [[Intel High Definition Audio]].

==AC-Link==
The AC-Link is a digital link that connects the DC97 (the controller) with the audio "codecs." It is composed of five wires: the 12.288&nbsp;MHz {{var|clock}}, a 48&nbsp;kHz {{var|sync}} signal, a {{var|reset}} signal, and two data wires which carry the actual audio data: {{var|sdata_out}} and {{var|sdata_in}}. The first four are outputs from the controller, while {{var|sdata_in}} carries input from the codec. The link carries a bidirectional serial data stream at a fixed bitrate (12.288&nbsp;Mbit/s) between the controller and one or more codecs.

Each 12.288&nbsp;Mbit/s stream is divided into 256-bit frames (frame frequency is 48&nbsp;kHz). This is therefore a [[time-division multiplexing]] scheme.

Every frame is subdivided in 13 slots. The first (slot 0) is 16 bits long and contains validity flags for the remaining slots, while the remaining 240 bits are divided in twelve 20-bit slots (slots 1–12), used as data slots.

Slots 1, 2 and 12 are used for non-audio data, while slots 3&ndash;11 carry up to nine channels of raw [[pulse-code modulation]] audio signals. Normally, six channels are used for 5.1 surround sound, and three channels are available for modem use. However, slots can be combined to provide a 96&nbsp;kHz sampling rate for the L, R and C channels.

Lower sample rates (such as 44.1&nbsp;kHz) are implemented using a [[Handshake (computing)|handshake protocol]] between the controller and codec which skips data during certain frames. (This capability depends on the codec. Alternatively, [[sample rate conversion]] could be performed in the DC97 (controller) or in the software driver.)

==Codec chips==
Codec chips have an AC'97 interface on one side and analog audio interface on the other. They are usually small square chips with 48 pins (48-pin [[Quad Flat Package|QFP]] package). They are D/A and A/D or only D/A.

* [[Analog Devices]] AD1819B, AD1881A, AD1885, AD1886, AD1887, AD1980, AD1981, AD1981A, AD1985. Since then, ADI have gotten out of the PC Audio business, either obsoleting or selling off devices to [[Conexant]],<ref>{{Cite news |last=Cyril |first=Kowaliski |date=December 15, 2008 |title=Analog Devices passes SoundMAX torch to Conexant |work=Techreport |url=https://techreport.com/news/16065/analog-devices-passes-soundmax-torch-to-conexant/}}</ref> (which is now [[Synaptics]]).
* [[AKM (Asahi Kasei Microsystems)]] AK 4540, 4543, 4544A, 4545
* [[Avance Logic]] (now [[Realtek]]) ALC201A, ALC202/A, ALC650, ALC655, ALC658, ALC101, ALC202A, ALC250, ALC850, ALC888
* [[Conexant]] Cx20468 - with a modem, 
* [[Cirrus Logic]] CrystalWare 4236, CrystalClear SoundFusion CS4297, CS4299
* [[Creative Technology]]
* [[Crystal Semiconductor]]s CS4205, CS4202
* [[C-Media]] CMI9738, 9739, 9761, 9880
* [[ESS Technology|ESS]] ES1988 (with a modem)
* Empia EMP202 (2 channel, 20-bit DAC and 20-bit ADC, full duplex AC'97 2.2 compatible stereo audio CODEC)
* [[Integrated Device Technology]] (IDT)
* [[Intersil]] HMP9701 (obsolete, 48&nbsp;kHz fixed sample rate)
* [[National Semiconductor]] LM4550, LM49321, LM49350, LM49352
* [[Philips]] UCB 1400 (with touchscreen controller)
* [[Realtek]] ALC5610 ALC5611<ref>[http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PNid=25&PFid=38&Level=4&Conn=3 AC'97 Interface] {{webarchive |url=https://web.archive.org/web/20120302112431/http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PNid=25&PFid=38&Level=4&Conn=3 |date=March 2, 2012 }}</ref><ref>[ftp://58.211.24.153/pc/caudio/ALC5610_DataSheet_1.4.pdf ALC5610 datasheet V1.4]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}}</ref><ref>[ftp://207.232.93.28/pc/caudio/ALC5611_DataSheet_1.3.pdf ALC5611 datasheet v1.3]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}}</ref>
* [[SigmaTel]] (now [[Integrated Device Technology|IDT]]) C-Major STAC 9460 (D/A only), 9461, 9462, 9463, 9200, 9202, 9250, 9251, 9220, 9221, 9223, 9750
* [[Silicon Labs]] Si3036, Si3038, Si3046, Si3048 (modem only, two part chipset consists of Si3024 or Si3025 and Si3012 or Si3014)
* [[TriTech Microelectronics]] TR28022, 28026
* [[Yamaha Corporation|Yamaha]] YMF 743, 752, 753
* [[VIA Technologies|VIA]] VT1612, VT1616 (VIA Six-TRAC Vinyl Audio)
* [[Winbond]] W83971
* [[Wolfson Microelectronics]] WM9701, WM9703, WM9704, WM9705 (w/touchscreen), WM9707, WM9708, WM9709 (DAC only), WM9711, WM9712 (w/touchscreen), WM9713 (w/touchscreen), WM9714

==Front panel connector==
Computer motherboards often provide a connector to bring microphone and headphone signals to the computer's front panel with [[Sound card#Color codes|standard color jack]]. Intel provides a specification for that header; the signal assignments are different for AC'97 and [[Intel High Definition Audio]] headers.<ref>{{Citation |last=Intel Corporation |url=http://www.formfactors.org/developer/specs/A2928604-005.pdf |title=Front Panel I/O Connectivity Design Guide |date=February 2005 |version=Version 1.3 |pages=19–25 |access-date=2008-02-06 |archive-url=https://web.archive.org/web/20110511144045/http://www.formfactors.org/developer/specs/A2928604-005.pdf |archive-date=2011-05-11 |url-status=dead }}</ref>

{{hatnote|For a comparison of pin assignments, see {{Section link|Intel High Definition Audio|Front panel connector}}.}}

==Operating system support==
AC'97 is supported by most operating systems, such as Windows (starting with [[Windows 95]]) and Linux. Under DOS, applications access the sound hardware directly instead of through the operating system, and most DOS applications do not support AC'97. 64-bit versions of Windows 7 and later require a third-party driver for AC'97 support.<ref>{{Citation|publisher=Oracle Corporation|year=2009|url=https://www.virtualbox.org/ticket/5332|title=VirtualBox Bug #5332}}</ref>

==See also==
{{Commons category}}
* [[Inter-IC Sound]] (I²S)
* [[Audio/modem riser]] (AMR)
* [[Advanced Communications Riser]] (ACR)
* [[Communications and networking riser]] (CNR)
* [[Mobile daughter card]] (MDC)
* [[Sony/Philips Digital Interface]] (S/P-DIF)
* [[PC System Design Guide]]
*[[Sound card]]

==References==
<references/>

{{PC sound standards}}

{{DEFAULTSORT:Ac'97}}
[[Category:Audio software]]
[[Category:Sound cards]]
[[Category:Computer-related introductions in 1997]]
[[Category:Computer hardware standards]]