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 ?
Figures 2 and 3 illustrate two active riser card designs that deploy multiple slots.
Regarding expansions, NCA-4210 is designed with an Ethernet NIC module socket at the front or with the option of a rear PCI riser card at the rear on the same side.
GVC, Puretek, Wellcom, and Pineview will deploy ESS's modem technology into desktop PCs as a PCI riser card, while Ambit and Actiontec will provide ESS softmodem mini-PCI modules to top-tier OEM customers in the United States, including Hewlett-Packard and Dell Computers.
A flexible riser card supports a variety of Fabric Interfaces including PICMG 3.
The RMC6224, utilizes an Intel[R] Xeon E3 Quad Core processor with Intel[R] C224 chipset on an industrial Micro ATX motherboard and features a built-in riser card with four low profile PCIe slots for expansion.
The Dell Precision 690-1KW workstation features an optional dual-graphics riser card that combine two NVIDIA(R) SLI(TM) graphics cards for increased performance and visual quality.
8DIMM slots and all DIMM slots are onboard without any riser card.
The specification defines the mechanical locations of the connectors, pinouts, signaling conventions, mechanical specifications for the 1U riser card and the HyperTransport daughtercard, and layout rules for motherboard, riser, and daughtercard.
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.
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.