| Introducing COM Express -- a new small form-factor for embedded computing |
by Rohit Chhabra (Feb. 8, 2005)
Forward: This whitepaper by a marketing manager in Intel's Infrastructure Processor Division introduces COM Express, a new "computer on module" (COM) standard from the PCI Industrial Computer Manufacturers Group (PICMG). COMs are tiny single-board computers (SBCs) that are used as macrocomponent-like building blocks in embedded systems, lessening the need for companies to design custom embedded processor subsystems.
The increasingly popular approach also avoids the requirement for complete system redesigns when embedded processors become obsolete, and facilitates upgrades to next-generation processors and features. But as the COM concept has gained popularity, there has been a proliferation of incompatible approaches and standards. With COM Express, PICMG hopes all that will change.
COM Express: The Next Trend in Embedded Computing Small Form Factors
by Rohit Chhabra
Overview: Computer-on-Module Methodology
Many of today's most innovative embedded application segments benefit from high levels of processing performance and I/O bandwidth in extremely compact form factors. Legacy interfaces including Peripheral Component Interconnect Extended (PCI-X) and Accelerated Graphics Port (AGP) can no longer satisfy the requirements of leading-edge applications in medical imaging, retail point-of-sale and advertising terminals, gaming, and industrial automation.
Meeting the requirements of these embedded market segments will require platform developers to gradually replace legacy parallel interfaces entirely with low-voltage differential signaling (LVDS) interfaces, while taking advantage of the performance gains enabled by new generations of processors and chipsets.
The continuing evolution of processors and the emergence of the current generation of high-speed serial differential interfaces confront embedded developers with the problem of how to implement these new capabilities while maintaining focus on their core business. Clearly, the task of engineering a new single-board computer (SBC) for each new generation of processors, or to implement faster buses, is an extremely expensive and time-consuming proposition. It can also place an added burden on already thinly stretched engineering resources.
Computer-on-Module, or "COM" methodology, has become a well-accepted way to implement many of the most demanding embedded solutions. COM can be simply defined as a module that contains all the components needed for a bootable host computer, packaged as an off-the-shelf component. System expansion and customization for each solution is implemented on an application-specific carrier board. Together, the COM and carrier board deliver the functionality of a single-board computer.
As the COM approach has gained in popularity, the embedded industry has recognized the need for an open COM standard to provide the advantages of modular, off-the-shelf building blocks. In addition, the industry saw the need for a standard that would enable a smooth transition from legacy interfaces, such as PCI and AGP, to legacy-free LVDS interfaces, including PCI Express, Serial ATA and Serial Digital Video Out (SDVO).
The answer is the COM Express specification from the PCI Industrial Computer Manufacturers Group (PICMG). With COM Express products beginning to appear in 2005, embedded developers interested in fast time to revenue should learn more about this robust, embedded industry standard.
COM Advantages
Small and rugged, Computer-on-Module implementations are ideal for a broad range of embedded applications where they fit mechanically, economically, and functionally, and where other form factors such as add-in cards cannot be used. For embedded developers the advantages of the COM methodology include faster time to market, better control over form-fit-function, reduced development cost and risk, and lower total cost of ownership through scalability.
Perhaps the greatest reason embedded developers have been attracted to the COM methodology is that it lets them focus their engineering resources on meeting core business requirements, without having to worry about how to implement new generations of processors and evolving I/O technologies.
Volatile demand fluctuations and intense competition are facts of life in the embedded world, and the COM approach enables system manufacturers to efficiently respond to competitive forces and meet new requirements by modifying their existing designs and expanding their product portfolios. This is especially true of embedded products with 5-to-10-year lifecycles whose compute performance and I/O capabilities must also be kept up to date.
The compelling advantages of the COM approach have given rise to a large base of suppliers who are working to meet the growing demand for COM modules and carrier boards. According to VDC, the COM and carrier board market segment is predicted to grow 54 percent annually through 2006 (source: Venture Development Corporation research, January 2004).
"Because of the interest generated by the COM approach, the embedded commercial segment is ready for a new standard that makes the computer-on-module an interchangeable component," said Jennifer Zickel, product marketing manager at RadiSys Corporation.
While the COM approach has grown in popularity, it has also engendered a proliferation of potentially incompatible COM products. In 2004, this situation prompted the industry to begin work on an open industry standard, known as COM Express.
COM Express
COM Express is the PICMG industry standard for Computer-on-Modules, developed with embedded industry participation under the sponsorship of Intel, Kontron, PFU, and RadiSys.
The goals of the COM Express standards effort include the creation of specifications for small-form-factor modules to satisfy all performance segments of the embedded industry. For example, high-performance segments can use COM Express to replace PCI-X and AGP with PCI Express and replace parallel ATA with Serial ATA. COM Express also provides a bridge between legacy-free and legacy functions by incorporating optional PCI and IDE interfaces.
According to Wade Clowes, vice president and general manager of RadiSys Commercial Segment, "COM Express makes it an order of magnitude easier to configure a range of embedded products. RadiSys customers will be able to offer a line of products from low-end to high-end, using the same carrier board and swapping-out the COM module."
COM Express is designed to help accelerate development in some of today's most dynamic application segments: - Retail and advertising -- electronic billboards, interactive kiosks and shopping carts
- Medical -- C-Arm real-time imaging and 3D/4D ultrasound devices
- Test and measurement -- bus and protocol analyzers and automated test equipment
- Gaming, entertainment and hospitality -- high-definition, media-rich gaming platforms
- Industrial automation -- nondestructive testers, 4D microscopy, volumetric imagers and real-time data analyzers
- Military/government and security -- unmanned vehicles, training simulators and portable tactical communications (C4) devices
In each of these market segments COM Express safeguards R&D investments and lowers total cost of ownership (TCO) by enabling designers to partition commodity host-processor COM Express modules from proprietary, value-added platform building blocks, including Field Programmable Gate Arrays (FPGAs) and specialty I/Os.
By improving form-fit-function in specific applications, COM Express modules can help minimize current and future design risks. It can help cut development time and costs during the initial phase of product development, while providing the scalability needed to cost-effectively implement value-added innovations over the multiyear lifecycle of an embedded platform.
Functional Overview
COM Express is designed as a CPU-agnostic standard that will enable the embedded industry to adopt all-LVDS interfaces, while maintaining support for legacy interfaces, as illustrated in Figure 1.
Figure 1
COM Express board-to-board connectors consist of two rows of 220 pins each. Row AB, which is required, provides pins for PCI Express, Serial ATA, LVDS LCD channel, LPC bus, system and power management, VGA and TV-out, LAN, and power and ground interfaces. Row CD, which is optional, provides SDVO and legacy PCI and IDE signals next to additional PCI Express, LAN and power and ground signals.
COM Express provides support for: - Up to 32 PCI Express lanes with 80-gigabit per second (Gbps) aggregate bandwidth
- External x16 PCI Express graphics
- Up to four Serial ATA-150 links with 600-megabyte per second (MBps) aggregate bandwidth
- Up to three 1-Gbps Ethernet ports, with provision for 10-Gbit Ethernet in the future
- Up to eight USB 2.0 ports
- Up to two channels of LVDS
- Up to two channels of Serial DVO
COM Express is also designed to accommodate the next generations of PCI Express (5 GHz) and Serial ATA (300 Mbps) interfaces, effectively doubling existing data rates to 160 Gbps and 1.2 GBps (gigabytes per second), respectively.
As shown in Figure 2, COM Express includes two module footprints, a compact Basic Form Factor measuring 125 mm x 95 mm and an Extended Form factor of 155 mm x 110 mm. These form factors share the same connector and signaling definitions and have overlapping mechanical assemblies. This makes it possible to interchange a Basic Form Factor module with an Extended Form Factor module, and vice versa. The Extended Form factor makes room for double the memory capacity and dual-channel memory configurations, in addition to larger processors and chipsets. Standardized height and heat spreaders further facilitate interchangeability between modules from different manufacturers.
Figure 2 COM Express footprint definitions, including Basic Form Factor (top) and Extended Form Factor (bottom)
The Extended Form Factor has a power budget of 160 Watts to support larger processors and chipsets. It also can accommodate dual-channel memory configurations. Standard height and heat spreaders facilitate interchangeability.
The form factor flexibility of COM Express enables developers to segment their designs for different classes of embedded applications, noted Kishan Jainandunsing, vice president of Technology and Business Development at PFU Systems. "The Basic Form Factor is extremely well suited for highly power sensitive, small devices such as portable applications for medical imaging and test and measurement. The Extended Form Factor is a good choice for mobile or stationary applications where performance is more important than low power dissipation, such as 4D ultrasound machines, arcade gaming devices, multimedia kiosks and electronic advertising billboards. Interchangeability between the two form factors is a bonus."
Summary
COM Express delivers the highest performance available on an extremely small embedded module. The most compelling advantage of the new standard is that it brings the benefits of standardization to the Computer-on-Module methodology, enabling embedded developers to keep pace with advances in processor architecture and serial interface technology without the need to reengineer their products for each successive generation of technology.
The ability to divide embedded systems into commodity and noncommodity partitions allows developers to focus their resources on value-added building blocks, while accelerating time-to-market and reducing development costs.
The availability of the COM Express specification through PICMG and broad industry participation will help to ensure the widespread adoption of this standard across a broad range of embedded applications. In the words of Kishan Jainandunsing of PFU Systems, "COM Express shields embedded developers from the intricacies of processor and chipset evolution, and it provides a smooth transition path to LVDS interfaces. The specification is designed to be applicable for a very long time, as PCI Express and Serial ATA are industry standards with a considerable life expectancy, and COM Express is formulated to accommodate the higher data transfer rates for next-generation PCI Express, Serial ATA, and Ethernet."
Embedded developers should order the specification through PICMG as soon as it becomes available in 2005 and join the growing community of COM Express solution providers.
More Info
 About the author: Rohit Chhabra is COM Express Initiative Manager, and Marketing Manager, Infrastructure Processor Division, Intel Corporation. Chhabra began his Intel career in 2000 as a product line manager in Hudson, Massachusetts managing PCI Bridges. In 2002, he moved to Chandler Arizona, where he held positions in product marketing and emerging country management. Chhabra was instrumental in the creation of the COM Express specification and directly involved in the success of the PCI Express, Serial ATA and Advanced Switching specifications. Prior to joining Intel, he worked for a vertically integrated manufacturer of high voltage connectors, servicing the medical equipment, X-ray and business machines industries. He earned a bachelor's degree in engineering from the University of Massachusetts, Amherst and obtained his M.B.A., magna cum laude, from Babson College.
Copyright © Intel Corporation 2005. All rights reserved. Reproduced by DeviceForge.com with permission. This article was originally published in Intel's Technology@Intel Magazine.
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