One significant advantage of the Intel® Architecture family of microprocessors is the many ways that embedded design teams can deploy modular systems based on those processors. The breadth of IA offerings in terms of performance, power consumption, and integrated functions such as graphics mean that manufacturers of board-level products typically support IA processors first on any new modular standard. I've written several times recently on modular standards for small form factors such as COM Express and EPIC. Today let's discuss the new CompactPCI PlusIO standard that targets high-performance applications such as simulators, medical systems, industrial controllers, and communications gear that are based on multiple larger boards.


The original CompactPCI standard defined a way to use the PCI bus developed by Intel for PC usage in industrial computers developed around the Eurocard format for 3U and 6U boards that are 5.25- and 10.5-inches high respectively. CompactPCI-based systems found broad usage in a wide range of applications including military, communications, medical, and industrial-control applications.


But parallel buses such as PCI began to hit a wall over the last decade. As such buses increased in speed, jitter became a problem. Moreover wider buses required more-complex PC boards, impacted the pin count of ICs, and required more complex connectors. Even though a serial interface must operate at a much higher clock rate to support the same bandwidth as a parallel bus, the serial option offers numerous benefits that make it the right choice. We've seen serial technology usurp PCI with PCI Express (PCIe). Moreover other interfaces such as the SATA (Serial ATA) interface used for disk drives made the transition from parallel to serial. And of course Ethernet was always serial in nature.


The key to high-performance systems based on a serial interface such as PCIe is a switch-based architecture that effectively provides point-to-point links between connected devices. Just as Ethernet moved to a switched architecture more than a decade ago, serial replacements for parallel-bus system interconnects rely on a switched fabric.


The move to PCIe also required a change or expansion of the CompactPCI spec to support the serial interfaces, and to support other serial interfaces such as SATA, USB, and Ethernet. CompactPCI systems needed a way to route the serial signals across the backplane.


The PCIMG industry group that promulgates the CompactPCI specification has taken multiple paths to supporting PCIe and other serial interfaces across a backplane. The CompactPCI Serial standard that's under development defines an entirely new connector and will provide a clean-sheet-of-paper approach to the issue while not offering backwards compatibility with boards built to the original specification.


CompactPCI PlusIO preserves compatibility with parallel CompactPCI boards while routing 4 PCIe x1 links, 4 SATA links, 4 USB 2.0 links, and 2 Ethernet links over connector pins originally left available for user-specific definition. In the near term, CompactPCI PlusIO will be a popular way for embedded teams to maintain legacy compatibility while taking advantage of the newest IA processors. For example, many industrial and military applications require custom boards that have been developed for CompactPCI.


If you are looking for more information on the topic, Manfred Schmitz of MEN Mikro Elektronik* posted a comprehensive article entitled "What is CompactPCI Plus" in the hardware section of the Intel® Embedded Community site. MEN Mikro also has a page on its web site on CompactPCI Serial/PlusIO.


As you might expect, you can already buy CompactPCI PlusIO products from several vendors. For example, MEN Mikro offers the F19P 3U board based on a 2.26-GHz Intel® Core™ 2 Duo SP9300 processor. The board delivers 4 PCIe, USB, and SATA links across the backplane and a single Ethernet link.






Emerson Network Power Embedded Computing** has also announced a CompactPCI PlusIO 3U board that's based on the Intel® Core™ i7 dual-core processor. The CPCI7203 board integrates as much as 4 Gbytes of DDR3 memory and 256 kbytes of non-volatile Ferroelectric RAM (F-RAM). Both Emerson and MEN Mikro also offer transition modules that make the various serial interfaces accessible at the rear panel of a system.


The CompactPCI PlusIO technology is already being deployed in systems. For example, Men Mikro Chief Marketing Officer Barbara Schmitz recently posted a blog about a camera-based surveillance system on the hardware section of this site.


How are you planning to support serial technology in embedded systems platforms? Do you have plans to use CompactPCI PlusIO or Serial in systems or have you already done so? Please share your experience and questions via comments with fellow followers of the Intel® Embedded Community.


Maury Wright

Roving Reporter (Intel Contractor)

Intel® Embedded Alliance



* MEN Micro Electronik Gmbh is an Affiliate Member of the Intel® Embedded Alliance

* Emerson Network Power Embedded Computing is a Premier Member of the Alliance