riser card

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riser card

(1) A printed circuit board for low-profile motherboards. The peripheral controller cards plug into the riser card and sit parallel with the motherboard. See low-profile motherboard.

(2) An expansion card that is used to physically extend a slot in order to make it easier to plug in the chip or card.

(3) A small PC expansion card that contains audio, modem and networking capabilities. When first introduced, it let manufacturers create custom systems for different audiences using motherboards that had none of these built-in functions. After audio and networking were built into the motherboard, risers were used for modems because they could be easily interchanged for international certification (homologation). See AC'97 and HD Audio.

Audio/Modem Riser (AMR)
AC'97 Audio, V.92 Modem
In 1998, Intel introduced software-driven audio and modem capabilities in the 46-pin AMR card as well as a Mobile Daughter Card (MDC) for portable solutions. Although motherboards were built with AMR slots, AMR offered little because it usurped a PCI connection, lacked Plug and Play and was software driven.

Communications and Networking Riser (CNR)
AC'97, V.92, Ethernet, HomePNA, USB
In 2000, Intel introduced the 30-pin CNR card, which added Plug and Play support and audio, modem and network functions. CNR included USB and took up one PCI slot. Ethernet and HomePNA connectivity was provided via the Intel LAN Connect Interface (LCI) or the Media Independent Interface (MIL).

Advanced Communications Riser (ACR)
AC'97, V.92, Ethernet, HomePNA, DSL
In 2000, AMD, 3Com and others introduced ACR to supersede AMR. Taking up one PCI slot, it accelerated audio and modem functions in hardware. For audio and modem only, it could be built with a connector to plug into an AMR slot. For networking, the card used a full PCI slot, colored blue and reversed.

ACR allowed modem, HomePNA and DSL to be connected over one telephone jack. It also supported multiple Ethernet controllers.

PC Motherboard Riser Cards
ACR cards can be designed to fit into AMR slots or PCI slots (blue and reverse from standard PCI).
References in periodicals archive ?
If a server only requires PCIe connectivity, then the problem of limited I/O expansion can be solved by placing a PCIe switch on the riser card, as in Figure 3.
Dual-graphics capabilities that support quad monitors or NVIDIA(R) SLI technology for enhanced graphics performance (available via an optional graphics riser card in a specially designed 1KW 690 chassis)
Molex Incorporated (Nasdaq: MOLX; MOLXA), a global electronic components company, and Silicon Image (Nasdaq: SIMG), a price/performance leader in high-bandwidth semiconductor solutions for mass markets, today unveiled the Molex MicroCross DVI Link riser card for desktop digital video.
Additional features include PCI riser card support to ease integration into rack-mount servers; 8 GPIO lines for cost-saving I/O control functions; integrated standard VGA; and enhanced Phoenix BIOS features for motherboard control and setup, and console redirection.
Being first is recognition of Smart Link's leadership in the Modem Riser Card form factor.
The rating system will be the first of its kind for an open standard and will improve the experience of ACR motherboard and riser card vendors as well as end users.
A CNR based on the Si3048 auto-configurable interface enables a complete Plug-and-Play (PnP) riser card that can be sub-system certified, allowing manufacturers to build a single riser card for use with any motherboard.
The CNR Specification defines a scalable motherboard riser card interface that supports broadband, multichannel audio, V.
The system bios of an ACR-compatible PC can communicate with the riser card, making it completely transparent to the computer's operating system.
Production samples and mini-PCI and PCI riser card reference designs are currently available.
Experts will discuss an array of topics including: IPB, EEPROM, motherboard layout and riser card design.
ACR is an open standard PC communications riser card specification, jointly promoted by VIA Technologies, Inc.