Riser architectures for motherboards

In the late 1990s, the PC industry developed a need for a riser architecture that would contribute towards reduced overall system costs and at the same time increase the flexibility of the system manufacturing process. The Audio/Modem Riser AMR) specification, introduced in the summer of 1998, was the beginning of a new riser architecture approach. AMR had the capability to support both audio and modem functions. However, it did have some shortcomings, which were identified after the release of the specification. These shortcomings included the lack of Plug and Play (PnP) support, as well as the consumption of a PCI connector location. Consequently, new riser architecture specifications were defined which combine more functions onto a single card. These new riser architectures combine audio, modem, broadband technologies, and LAN interfaces onto a single card. They continue to give motherboard OEMs the flexibility to create a generic motherboard for a variety of customers. The riser card allows OEMs and system integrators to provide a customised solution for each customer’s needs. Two of the most recent riser architecture specifications include CNR and ACR. CNR – Communications and Networking Riser Intel’s CNR (Communication and Networking Riser) specification defines a hardware scalable OEM motherboard riser and interface that supports the audio, modem, and LAN interfaces of core logic chipsets. The main objective of this specification is to reduce the baseline implementation cost of features that are widely used in the Connected PC, while also addressing specific functional limitations of today’s audio, modem, and LAN subsystems. PC users’ demand for feature-rich PCs, combined with the industry’s current trend towards lower cost, mandates higher levels of...

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