AC'97 (''Audio Codec '97;'' also MC'97 for ''Modem Codec '97'') is an

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...

codec standard developed by

Intel Architecture Labs __NOTOC__ Intel Architecture Labs (IAL) was the personal-computer system research-and-development arm of Intel during the 1990s. History and formation IAL was created by Intel Vice-president Ron Whittier together with Craig Kinnie and Steven M ...

in 1997. The standard was used in

motherboard A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...

modem A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...

s, and sound cards. The specification covers two types of components, and the AC-Link digital interface between them: # an AC'97 ''digital controller'' (DC97), which is built into the southbridge of the chipset, and # an AC'97 audio and modem ''codec'', available from several vendors, which contains the analog components of the architecture. AC'97 defines a high-quality, 16- or 20- bit audio architecture with

5.1 surround sound 5.1 surround sound ("five-point one") is the common name for surround sound audio systems. 5.1 is the most commonly used layout in home theatres. It uses five full bandwidth channels and one low-frequency effects channel (the "point one"). Dolb ...

support for the PC. AC'97 supports a 96 kHz

sampling rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or spac ...

at 20-bit stereo

resolution Resolution(s) may refer to: Common meanings * Resolution (debate), the statement which is debated in policy debate * Resolution (law), a written motion adopted by a deliberative body * New Year's resolution, a commitment that an individual mak ...

and a 48 kHz sampling rate at 20-bit stereo resolution for multichannel recording and playback. Integrated audio is implemented with the AC'97 Codec on the

, a communications and networking riser card, or an audio/modem riser card. In 2004, Intel released Intel High Definition Audio (HD Audio) which is a successor that is not backward compatible with AC'97. 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 7.1 surround sound is the common name for an eight-channel surround audio system commonly used in home theatre configurations. It adds two additional speakers to the more conventional six-channel (5.1) audio configuration. As with 5.1 surround sou ...

Revisions

AC'97 has had several revisions: * AC'97 1.x compliant indicates fixed 48 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 Sony/Philips Digital Interface Format * AC'97 2.3 compliant indicates extended configuration information and optional

jack sensing Jack may refer to: Places * Jack, Alabama, US, an unincorporated community * Jack, Missouri, US, an unincorporated community * Jack County, Texas, a county in Texas, USA People and fictional characters * Jack (given name), a male given name, ...

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 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 MHz , a 48 kHz signal, a signal, and two data wires which carry the actual audio data: and . The first four are outputs from the controller, while carries input from the codec. The link carries a bidirectional serial data stream at a fixed bitrate (12.288 Mbit/s) between the controller and one or more codecs. Each 12.288 Mbit/s stream is divided into 256-bit frames (frame frequency is 48 kHz). This is therefore a

time-division multiplexing Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fracti ...

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 3–11 carry up to nine channels of raw

pulse-code modulation Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the ...

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 kHz sampling rate for the L, R and C channels. Lower sample rates (such as 44.1 kHz) are implemented using a

handshake protocol A handshake is a globally widespread, brief greeting or parting tradition in which two people grasp one of each other's like hands, in most cases accompanied by a brief up-and-down movement of the grasped hands. Customs surrounding handshakes a ...

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

QFP A quad flat package (QFP) is a surface-mounted integrated circuit package with "gull wing" leads extending from each of the four sides. Socketing such packages is rare and through-hole mounting is not possible. Versions ranging from 32 to 304 ...

package). They are D/A and A/D or only D/A. *

Analog Devices Analog Devices, Inc. (ADI), also known simply as Analog, is an American multinational semiconductor company specializing in data conversion, signal processing and power management technology, headquartered in Wilmington, Massachusetts. The co ...

AD1819B, 1881A, 1885, 1886, 1887, 1980, 1981, 1985 *

AKM (Asahi Kasei Microsystems) The AKM () is an assault rifle designed by Soviet small arms designer Mikhail Kalashnikov in 1959. It is the most ubiquitous rifle of the Kalashnikov rifles. It was developed as a replacement to the AK-47 introduced a decade prior. Introduced ...

AK 4540, 4543, 4544A, 4545 *

Avance Logic Realtek Semiconductor Corp () is a fabless semiconductor company situated in the Hsinchu Science Park, Hsinchu, Taiwan. Realtek was founded in October 1987 and subsequently listed on the Taiwan Stock Exchange in 1998. Realtek currently manufactu ...

(now

Realtek Realtek Semiconductor Corp () is a fabless semiconductor company situated in the Hsinchu Science Park, Hsinchu, Taiwan. Realtek was founded in October 1987 and subsequently listed on the Taiwan Stock Exchange in 1998. Realtek currently manufactu ...

) ALC201A, ALC202/A, ALC650, ALC655, ALC658, ALC101, ALC202A, ALC250, ALC850, ALC888 *

Conexant Conexant Systems, Inc. was an American-based software developer and fabless semiconductor company that developed technology for voice and audio processing, imaging and modems. The company began as a division of Rockwell International, before bei ...

Cx20468 - with a modem *

Cirrus Logic Cirrus Logic Inc. is an American fabless semiconductor supplier that specializes in analog, mixed-signal, and audio DSP integrated circuits (ICs). Since 1998, the company's headquarters have been in Austin, Texas. The company's audio processo ...

CrystalWare 4236, CrystalClear SoundFusion CS4297, CS4299 *

Crystal Semiconductor Cirrus Logic Inc. is an American fabless semiconductor supplier that specializes in analog, mixed-signal, and audio DSP integrated circuits (ICs). Since 1998, the company's headquarters have been in Austin, Texas. The company's audio processo ...

s CS4205, CS4202 *

C-Media C-Media Electronics, Inc. () is a Taiwan computer hardware company that manufactures processors for PC audio and USB storage, and wireless audio devices. Products ISA audio * CMI8328 * CMI8330 PCI audio * CMI8338 * CMI8738-SX * CMI873 ...

CMI9738, 9739, 9761, 9880 *

ESS The suffix ''-ess'' (plural ''-esses'') appended to English words makes a female form of the word. ESS or ess may refer to: Education * Ernestown Secondary School, in Odessa, Ontario * European Standard School, in Dhaka, Bangladesh Governmen ...

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) *

Intersil Intersil is an American semiconductor company headquartered in Milpitas, California. As of February 24, 2017, Intersil is a subsidiary of Renesas. The previous Intersil was formed in August 1999 through the acquisition of the semiconductor busin ...

HMP9701 (obsolete, 48 kHz fixed samplerate) *

National Semiconductor National Semiconductor was an American semiconductor manufacturer which specialized in analog devices and subsystems, formerly with headquarters in Santa Clara, California. The company produced power management integrated circuits, display drive ...

LM4550, LM49321, LM49350, LM49352 *

Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...

UCB 1400 (with touchscreen controller) *

ALC5610 ALC5611 * SigmaTel (now IDT) C-Major STAC 9460 (D/A only), 9461, 9462, 9463, 9200, 9202, 9250, 9251, 9220, 9221, 9223, 9750 * Silicon Image Si3024 (mono only) * TriTech Microelectronics TR28022, 28026 *

Yamaha Yamaha may refer to: * Yamaha Corporation, a Japanese company with a wide range of products and services, established in 1887. The company is the largest shareholder of Yamaha Motor Company (below). ** Yamaha Music Foundation, an organization estab ...

YMF 743, 752, 753 *

VIA Via or VIA may refer to the following: Science and technology * MOS Technology 6522, Versatile Interface Adapter * ''Via'' (moth), a genus of moths in the family Noctuidae * Via (electronics), a through-connection * VIA Technologies, a Taiwan ...

VT1612, VT1616 (VIA Six-TRAC Vinyl Audio) *

Winbond Winbond Electronics Corporation () is a Taiwan-based corporation founded in 1987. It produces semiconductors and several types of integrated circuits, most notably Dynamic RAM, Static RAM, Serial flash, microcontrollers, and personal computer ...

W83971 *

Wolfson Microelectronics Wolfson Microelectronics plc was a microelectronics and fabless semiconductor company headquartered in Edinburgh, Scotland. It specialised in signal processing and mixed-signal chips for the consumer electronics market and had engineering and s ...

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 standard color jack. Intel provides a specification for that header; the signal assignments are different for AC'97 and Intel High Definition Audiobr>headers

Operating system support

AC'97 is supported by most operating systems, such as Windows (starting with

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to ...

) 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.

References