Practical design considerations -- Ethernet vs. RapidIO standards

By Tom Cox, RapidIO Trade Association
August 15, 2007 -- pldesignline.com

Engineers often discover ways to leverage technology in applications for which it was never intended. Sometimes the fit is "good enough" and the resulting economies of scale are sufficient to make the extended technology implementation successful. But the desire to use a familiar technology runs the risk of stretching the technology beyond its capabilities, complicating designs and creating unforeseen problems.

For example, Ethernet is frequently considered a prime candidate for the convergence protocol in system-level fabrics, yet comparing the familiar Ethernet to the RapidIO specification for board- and chassis-level applications can be surprising.

Ethernet was designed for large networks with many endpoints, each with a powerful processor available for protocol stack processing. RapidIO technology was designed specifically for embedded in-the-box and chassis control plane applications, and emphasizes reliability with minimal latency, limited software dependence, protocol extensibility, and simplified switching that provides effective data rates from 667 Mbps to 30 Gbps. Additionally, RapidIO technology features hardware-based protocol processing, support for read/write operations, messaging, data streaming, HWQoS, data plane extensions, and protocol encapsulation.

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