CSD 2018
Where’s the bus going?
By Jesse Winters
The VME bus (IEEE 1014-1987) and CompactPCI, two technologies based on open standards, are irreversibly changing the profile of
communication platforms. The VME bus literally opened the door for open standards in the communication rack. Although VME bus-based communication systems will continue to be deployed for years to come, CompactPCI has many attractive features that make it the heir apparent, such as 6U form factor, high bandwidth across the backplane, and new high availability features, such as hot-swap capability. CompactPCI is already being designed into all types of telecommunication systems, including next-generation PBX systems,
wireless basestation controllers, service control points, interactive voice response applications, and so on. A key incentive for the system designer is its relatively low cost.
CompactPCI’s inherent PCI interface frees the designer from the constraints of specific processor architectures, and allows the designer to capitalize on the abundance of new interface ASICs, intelligent microcontrollers, and off-the-shelf software. Expect to see more companies jumping on the CompactPCI bandwagon, motivated by
features designed for relatively rugged environments (as compared to PCI), such as better backplane and front panel connector designs, a form factor designed for telecom racks, future high availability features, and inevitable increases in bus speeds and data path widths.
Benefiting from the wide variety of off-the-shelf PCI interface components, CompactPCI is a nearly ideal bus architecture for new communication systems where low cost and high availability can both be achieved. A significant
commonality between VME bus and CompactPCI systems is the ability to utilize PCI mezzanine cards (PMC, IEEE P1386.1). The same PMC card can be used in either architecture via an appropriate carrier board. This represents an attractive economy of scale for the PCI board manufacturer. PMCs potentially reduce the number of spare parts that must be stocked, and create a more Lego-like building block system architecture that can be upgraded literally on the fly — assuming its carrier board is hot-swap enabled.
All
indications are that the demand for increased bandwidth will continue to spiral as more users find novel and innovative ways to exploit the Internet. Near real-time remote medical diagnostics — even arthroscopic surgery — could conceivably be performed remotely using video and robotics control messaging via ATM. Similarly, imagine real-time, high-fidelity recording sessions between musicians on both coasts via xDSL. Emerging markets will deploy wireless voice and data service to the most distant
corners of their territory using low-orbit satellites. All this on top of the rapid increase in demand for high-capacity corporate frame relay “extranets,” regional info-centers, and streaming commercial video feeds. The application possibilities are limited only by the creativity of the human mind — and every carrier is preparing for the onslaught. Already, a two- or three-line household is not uncommon, especially when including cellular telephones.
Open architecture platforms based on
VME bus and CompactPCI are improving the ability of communication infrastructure equipment suppliers to keep up with the ever-expanding bandwidth blitzkrieg.
As more products become available, CompactPCI will garner even more design wins, partially at the expense of cheaper, but less functional PCI systems, or the displacement of low-end VME solutions. However, don’t write off the VME bus any time soon. CompactPCI doesn’t inherently support an indivisible test-and-set instruction, so loosely
coupled multiprocessor systems require that locking be managed at a higher level. High availability systems at CompactPCI price points will be compelling, but it’s too early to tell if they will ever totally replace truly fault tolerant, “five 9s” types of systems (those offering 99.999% up-time).
Nevertheless, CompactPCI is just beginning to make its presence known, and there is little doubt it has a long and bright future for years to come.
Jesse Winters is communication products
manager for technical systems at Motorola Computer Group. He has a BS in Computer Science from the University of Kansas, KS. He can be reached at jesse_winters@mcy.mot.com.
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