Industry Insights

Interworking: Solidifying the Complementary Roles of PCI Express, RapidIO and Ethernet in Next Generation Systems

By Ernie Bergstrom, VP Research & Chief Analyst, Crystal Cube Consulting LLC

Crystal Cube Consulting (CCC) in its review of Next Generation Networks (NGN) and their development have monitored and tracked the major high-speed switch fabric architectures including RapidIO, Advanced Switching Interconnect (ASI), which recently became lifeless for the foreseeable future, InfiniBand, HyperTransport and Fibre Channel since 2003. It has been clear to us the direction that RapidIO has taken since the beginning, which was to set their sights on providing a transparent high-speed bus architecture aimed at delivering multiple connectivity and interoperability utilizing switching architecture as the control point for I/O connectivity. To that end RapidIO has taken a very obvious commanding lead in the high-speed bus architecture for embedded system. So with the announcement that Intel's ASI was being abandoned by a majority of its supporters, RapidIO was truly elated and well prepared to embrace their business model to address support for PCI Express and Ethernet.

Since its first inception, RapidIO has developed an eco-system of components and suppliers which provides the technology for the complementary roles of PCI Express along with RapidIO and Ethernet. Serial RapidIO switches decrease overall system cost, power and latency while providing distributed processing locally for DSPs and CPU's. The key advantages utilizing Switched Serial RapidIO architectures include low and deterministic latency between processing elements with lower power and low cost interconnect. Multicast support provided by RapidIO is another critical area for reducing latency in such applications as wireless base-band and video devices.

Currently CCC, with the research we have continued to do in the switch fabric architecture arena, see a definite heating-up of switch fabric architecture activity, if you will, in the communications sector between PCI Express and the competing Serial RapidIO interconnect supported by Freescale Semiconductor, Texas Instruments, Tundra and others. Unlike ASI, RapidIO is gaining traction as an interface for PowerPCs and digital signal processors, especially as a way to link the farms of DSPs found in wireless base stations and video.

The RapidIO Trade Association has created strong ties with tier-one OEMs. Last fall, representatives from Lucent Technologies, Ericsson and storage company EMC were elected as association officers. Several companies appear to be at the point where they plan to make commitments with RapidIO and are not likely to use ASI. Even if some companies were electing to revisit ASI in the future, as a possible high-speed switch fabric architecture, it appears to CCC that it would be some time before ASI could have a viable plan in place for high-speed architecture solutions for embedded systems.

There are those out there, however, that believe the rising adoption of PCI Express could have some market impact on RapidIO. PCI Express has such a large eco-system that some companies are recommending that people put native PCI Express interfaces on their communications chips. The situation seems to be that companies, in being prudent, need to consider how many DSPs will add PCI Express in the future. If that were to become quite common it could have an impact on RapidIO's continued strong growth, but that remains to be seen. Nevertheless with ASI stepping aside, and remembering ASI was to solve the shortcomings of a PCI Express solution in a fabric architecture, certainly puts RapidIO is in a very strong position in the market place.

One of the RapidIO member companies, Applied Micro Circuits Corp (AMCC) sells a PowerPC 440SPE processor that sports three Express interfaces and is geared for storage systems. It will announce its first CPUs with serial RapidIO before the end of the year, and also plans more devices using PCI Express. They are doing PCI Express, Ethernet and Serial RapidIO, and are the three interfaces that will be the processors of choice going forward, according to Sam Fuller, vice president of marketing at AMCC. Freescale ships a half dozen PowerPCs and one DSP using Serial RapidIO. Texas Instruments has two high-end DSPs using Serial RapidIO.

The flexibility that RapidIO offers with their serial switch fabric allows them to produce different products from the same hardware and software architecture, as well as the scalability to produce different classes of products with the same hardware and software architecture. Additionally, RapidIO can and will provide connectivity in their switch fabric architecture solutions to include PCI Express and Ethernet where the solution makes sense or is in the client's best interest. Flexibility is the name of the game for RapidIO's success moving forward.