COM Express subcommittee talks R2.1

2Revision 2.1 of the PICMG COM Express specification was adopted this May, so CompactPCI, AdvancedTCA & MicroTCA Systems sat down with key members of the subcommittee for a closer look at COM Express.

CPCI: First, what value do COMs provide developers?

BOEHMAN, AMD: COMs provide developers with several key values, but the most significant is the unique blending of COTS availability with customized feature sets. Modules are available from many vendors in a multitude of configurations supporting many different silicon solutions. Developers who need customized features or form factors need only design the carrier board with needed I/O connections. Most of the complexity is contained in the module, so this significantly reduces development risk and speeds time to market. The majority of module vendors also offer standard carrier boards and customization services, so even this effort can be avoided.

The second major benefit to COMs is easy upgradeability. Moving your semi-custom design to the next generation of compute engine can be as simple as ordering a new module and snapping it into place. Few solutions offer this kind of flexibility and future proofing.

PEBLY, : The primary benefit of a COM, especially in embedded applications, is the decoupling and modularization of the most complex and rapidly changing portion of an embedded design – the processor complex – from the rest of the system design. Instead of worrying about the constant tick-tock advances in processor and memory technology, developers can focus on the unique system aspects and I/O requirements of their application because the comfortable backing of a broad range of available COM modules allows the processing capability to be scaled to their solution. The COM approach removes the burden of getting the processing power dialed in just right early in the project, and allows developers to fine tune and adjust much later in the design and development process, while also providing a future path for simple upgrades driven by Moore's Law.

MUNCH, ADLINK: In a COM architecture, a developer can quickly and easily design a carrier board that is specific to the developer's application. The carrier can contain special application-specific silicon, , custom interconnects, custom form factors, or other features. Once designed, the carrier can be used with off-the-shelf COMs, each of which can be used on many different carrier boards. COM standards ensure interoperability among multiple vendors, and an ability to scale from low-power, low-performance processors to high-power, high-performance processors without redesigning the carrier. The COM approach also provides protection, as a previous generation COM can be replaced with a current generation COM without a carrier redesign. The COM architecture allows a developer to focus on their core competency – not the design, manufacture, and support of processor boards.

EDER, congatec AG: Value equals faster time-to-market. COMs provide reduced development costs, scalability of product (by way of CPU speeds, memory support, and so on), and security, so long as the COM is an industry standard. Being an industry standard assures second source availability and provides OEMs with the ability to focus on core competencies, versus designing PCs in house.

CPCI: What is the background and what are its benefits over other COMs?

MILNOR, : Prior to the development of COM Express, Kontron pioneered a very successful Computer-On-Module standard called Embedded Technology eXtended (ETX). It was essentially ISA and PCI-based and became a de facto embedded industry standard. In 2004, it became apparent that something beyond ETX was needed, and Kontron started working on a PCIe-based module called ETXexpress. Kontron management was also interested in getting support for another new module standard from Intel. Intel's response was that they wanted Kontron to take the standard to an independent standards body, and Kontron presented the idea to .

BROSS, Intel: A number of embedded ecosystem vendors recognized the value in standardizing a COM built around the high-speed differential signaling mechanisms that were emerging. Intel, Kontron, PFU Systems, and Radisys sponsored the original COM Express effort within PICMG, but dozens of companies have adopted COM Express and continue to develop COM Express products. Unlike some approaches that had been built around lower-speed, single-ended signals, COM Express was designed for high-speed signaling from the start, with robust connectors that could hold up to some of the most extreme conditions and most demanding signal rates.

BOEHMAN, AMD: The COM Express standard was first released in 2005 by the PCI Industrial Computer Manufacturers Group (PICMG) and it sought to provide standardized module interfaces for several different target applications. It did so by defining five different module "Types" each implementing different pinout configurations and feature sets on one or two 220-pin connectors. In that way, COM Express is a standard of multiple standards. It also defined 2 module sizes (later expanded to 4) to allow additional flexibility to better serve the end application while maintaining compatibility within each module "Type." Carrier boards can even be designed to support multiple module types. The benefit is a single design standard with a high degree of flexibility and usability across a wide range of applications. COM Express is applicable to designs ranging from large industrial computers to small hand-held devices, supporting power ranges from zero to 144W. The differing module types support many legacy interfaces like PCI and IDE for applications that require them, to the latest interface technologies including PCI Express and DisplayPort. Other COM standards tend to focus on a single pinout and modules of fixed size, which greatly limit their potential applications.

MUNCH, ADLINK: COM Express does not try and take a one-size-fits-all approach to the market. The authors of COM Express could see that different applications might require different features. The solution was to define multiple "Types" of COMs. Each Type had a slightly different feature set. Some in the industry have tried to attack this flexibility as being a sign of indecisiveness by the authors of the specification, when in reality it was insightful – would we all want to be forced to drive the same car regardless of our needs? Another major differentiator is that COM Express is maintained by PICMG, which has strict rules on the requirements for a change to the specification. Other COMs are held by standards organizations that are nothing more than a single company that can change the standard at will.

COM Express has also grown over time. The first revision was released eight years ago and refreshed five years later. The standard has evolved to meet the continuing needs of the market. There are other standards that are the same today as they were eight years ago; they claim this is an example of “stability.” I am glad the manufacturer of my laptop did not believe in this approach. In all, COM Express has a large ecosystem of suppliers serving a thriving user market – that is success.

PEBLY, Radisys: The COM Express specification carefully balanced the legacy interfaces needed for backward compatibility and support for newer, high-speed serial interfaces, enabling COM Express to quickly grab a large share of the COM market. In addition, the strength and backing of PICMG provided the solid, open standards foundation and processes for COM Express to differentiate itself from the plethora of self-branded COM and small form factor standards that littered the embedded market. The evolution of COM Express in 2010 with a major 2.0 revision, and now the minor Revision 2.1 (R2.1) in 2012, demonstrate the continued health and vibrancy of the specification. COM Express continues to keep pace with evolving technology trends while maintaining a strong focus on the backward compatibility necessary to enable a smooth migration path for current and future designs.

REUGER, Advantech: COM Express is an official industrial standard released by PICMG, meaning that all COM Express vendors will follow this standard, which ensures that customers can exchange COM Express modules between different vendors. This provides a flexibility that other COM form factors are not able to provide.

CPCI: Recently, R2.1 introduced form factor and silicon upgrades. What were those and what benefits do they provide over previous revisions?

MILNOR, Kontron: The main purpose of R2.1 was for the PICMG COM.0 document to officially sanction the credit card-sized 84 mm x 55 mm Mini form factor (Figure 1). Kontron developed this form factor some years ago outside of PICMG and referred to it as "COM Express compatible" (the pinout was 100 percent COM Express Type 1, but the form factor was smaller, hence “compatible”). Several companies joined Kontron in providing this form factor to the market under the “nano” marketing name. It gained enough market traction that the PICMG COM Express community saw advantages to folding it into the specification with an extended power input range.

Figure 1: The new COM Express “Mini” module provides a new form factor with an increased input voltage range, targeted at small form factor battery-powered applications, among others.

EDER, congatec AG: The major step was the upgrade from R 1.0 to R 2.0. This brought the Compact (95 mm x 95 mm) size and two new pinouts. The Type 6 pinout was a major step, and provided the perfect replacement for the current main Type 2 pinout. It trades the outdated 32-bit PCI and IDE interfaces with 3 Digital Display Interfaces (DDIs) that can be configured as DisplayPort or Transition-Minimized Differential Signaling ((TMDS) for HDMI or DVI)), four USB 3.0 links, and two additional PCI Express lanes (up to a total of 8 lanes). It also removed the Type 2 typical of SDVO and PEG, both of which are now available separately.

MUNCH, ADLINK: R2.1 was a minor rev' roll from R2.0. The biggest advances were from R1.0 to R2.0, when we picked up three digital display interfaces, support for PCI Express Gen 2, and defined a common set of software APIs for vendor-specific functions. In R2.1, the big change was support for small form factor battery-powered applications.

Initial COMs were powered by a 12 V supply. This was fine for most applications, but as the market for small, battery-powered devices matured it was clear that we needed to be more flexible in the input power for a COM to prevent the need for a front-end DC-DC converter. Therefore, in R2.1 we defined a smaller size module with a wide 4.75 V to 20 V input power supply range.

PEBLY, Radisys: In addition to the smaller form factor, R2.1 also added optional support for several new interfaces – CAN Bus, USB 3.0, and embedded DisplayPort (eDP). Each of these interfaces is important in expanding the applicability and reach of COM Express. CAN Bus enables COM Express as a solution in automotive applications while eDP enables lower cost display configurations for embedded applications. USB 3.0 keeps COM Express up to date with the evolution of USB and enables COM Express to support the latest SuperSpeed USB devices.

The addition of the Mini module allows COM Express to further expand its applicability and reach by addressing the constantly shrinking footprints required in today's embedded devices. It also broadens the spectrum and scalability of COM Express processing solutions by expanding the portfolio to more effectively enable newer low-power Systems-on-Chip (SoCs) from multiple vendors.

EDER, congatec AG: The additional "Mini" mechanical form factor defined in R 2.1 will be used for the reduced Type 10 pinout. This combination is meant for mobile applications, and its feature set is very comparable to the well-established Qseven definition. These updates have not only made COM Express more up to date, but have allowed the scalability of COM Express to increase. COM Express is tracking the silicon vendors quite effectively.

CPCI: How do these additions and improvements ensure COM Express is equipped for the evolution of processors and high-speed I/O interfaces?

PEBLY, Radisys: Current trends in embedded processors are all about smaller, lower-power, more highly integrated devices. The new Mini module enables COM Express to better support the increasing demands for smaller, lower power modular computing solutions based on SoCs. The original COM Express specification was already ahead of the game and made the jump from slower legacy parallel interfaces to higher-speed differential serial interfaces. R2.1 continues that trend with added support for USB 3.0, bringing a more than 10 times improvement to the now-ubiquitous serial interface maximum transmission speed.

REUGER, Advantech: It is clear that COM.0 R 2.1 is designed for all new technology from major chip vendors. Intel and AMD have joined the discussion in R2.1, ensuring that the high-speed I/O interfaces, such as PCI Express, USB 3.0, DisplayPort, and SATA 3 make COM Express more fit for customer demands.

BROSS, Intel: R2.0 of the COM Express specification went a long ways toward ensuring that high-performance compute modules support the signaling interfaces on today's latest processors and chipsets. R2.1 extended this high-speed signaling on the single-connector Type 10 definition, allowing USB 3.0 ports to be used over previously reserved signals. In another forward-looking move, COM Express R2.1 added support for eDP as an overlay for the legacy LVDS display signals that have long been a stalwart in the embedded community, but are being phased out by Intel and other CPU vendors over the next few years. The COM Express committee is also currently evaluating support for PCI Express Gen 3 and DisplayPort 1.2 signaling rates.

MILNOR, Kontron: A lot of effort went into picking the COM Express connector in 2004/2005 and in defining the pinout in an effort to anticipate where the x86 architecture was going. I think we did a good job, and the specification has held up well. With R2.0, the specification was updated by introducing the "Type 6" pinout, allowing the phase out of PCI and PATA in favor of new digital display interfaces, more PCIe, and USB 3.0. The original COM Express connector was selected for its pin density and its high bandwidth capabilities, and it is routinely used for PCIe Gen 2 and USB 3.0. Now, when 10 GHz signaling becomes mainstream, it will be time for a new module connector, but that seems to be a ways off, and, seven years after launch, there seem to be many years of life left in COM Express.

BOEHMAN, AMD: The architecture of the COM Express standard and its use of module "types" allows it to continuously evolve to support new technologies. While some new types break compatibility with earlier ones, they still leverage existing module infrastructure and design details. With major silicon providers actively involved in its specification development, the COM express standard also benefits from significant foreknowledge of processor product feature sets.

EDER, congatec AG: The evolution of the specification is following the silicon roadmaps to a "T." COM Express has been well received in the marketplace, and this evolution is only natural. Although the buses and I/O available might have changed a bit, the general concept of designing in a COM Express module has not. This keeps the learning curve short for designers as they move to the latest and greatest silicon.

CPCI: What is the current market share for COM Express, and what are its brightest markets and applications moving forward?

PEBLY, Radisys: According to VDC Research's 2011 report, the COM market will be $674 million in 2013, growing to $882 million in 2015. COM Express modules represent more than 85 percent of this market and are growing at a rapid pace. Some of the brightest markets for COM Express are the Industrial Automation and the Aerospace and Defense markets, which make up more than a third of the 2013 COM market.

Industrial Automation has historically been a large user of either small custom or small COM modules, but the basic and extended sizes were too large and expensive to fit into many applications. The introduction of the Compact (95 mm x 95 mm) and Mini COM Express specifications combined with newer low-cost, low-power processors has primed this segment for additional growth.

The Aerospace and Defense market is driving a need for higher processing performance, as equipment such as in-vehicle equipment is consolidated and designed to host multiple informational displays. In addition, the processing power of a COM Express module has increased to the point where it can be combined with 3G and software to be used for a portable cellular base station, either carried in a soldier's backpack or on a vehicle. The stability of the COM Express architecture, the benefit of future technology insertions, and the introduction of -40 ºC to +85 ºC extended temperature range COM Express modules are enabling an adoption explosion in this market segment. In addition, the smaller-sized Compact and Mini modules combined with extended temperature range enable the use of these modules in man-wearable or handheld devices used in the battlefield.

Another strong segment for the COM Express market is the Medical segment, where COM Express is being adopted as a common platform architecture. Medical imaging companies are designing carriers using COM Express, enabling their equipment to scale from the high-performance quad-core Intel i7 processors for cart-based systems to the low-power, low-cost Atom processors for handheld or portable systems.

BROSS, Intel: The sheer number of vendors providing COM Express modules and carriers attests to the strength of the COM Express market. Historically, we've seen embedded vendors come out with COM Express modules within about a year of silicon introduction, but we're now seeing several vendors introducing COM Express modules within a quarter of silicon release or even concurrent with Intel's CPU releases. Given the modular nature of COM Express systems, this means that carrier boards designed to use modules with last year's silicon can easily incorporate newer COM Express modules with this year's silicon if it suits the application. Some of the most exciting applications for COM Express modules include Machine-to-Machine ()/Internet of Things (IoT) applications, Industrial Automation, slot machines, sonogram machines/medical equipment, in-flight entertainment systems, and a number of military applications.

EDER, congatec AG: COM Express is congatec's largest currently install base, and I suspect it is the same for most of the other premier COM vendors as well. COM Express fits nicely into many vertical markets such as medical equipment, automation systems, digital gaming, digital signage, portable computing, and the like. I believe there is still a vast untapped market for COMs, with a lot of companies out there designing their own PC-based platforms. Every year more and more of them are introduced to COM Express and the other various industry COM specifications. The pie is continuing to grow.


Ben Boehman, Technical Marketing Manager, AMD: Ben Boehman is a Technical Marketing Manager at Advanced Micro Devices.

Kevin Bross, Modular Systems Architect, Intel: Kevin Bross is Intel's primary representative to PICMG and has been involved in all COM Express standards-related activities over the last five years.

Christian Eder, Marketing Manager, congatec AG: Christian Eder was the Editor of both the PICMG COM Express R2.0 and R2.1 specifications, as well as the PICMG COM Express Design Guide R1.0.

Stefan Milnor, VP of Engineering, Kontron: Stefan Milnor has been the primary Kontron representative to the PICMG COM Express subcommittee since its inception in 2004. He was the Draft Editor for the original COM.0 effort, and co-authored the original document. He is also the Editor of the original PICMG COM.0 Design Guide.

Jeff Munch, CTO, ADLINK: Jeff Munch plays an active role in PICMG, including chairing both the COM Express Plug-and-Play and COM Express R2.1 subcommittees.

Bob Pebly, CTO Fellow, Radisys: Bob Pebly is Radisys' primary representative in PICMG and has served in a variety of officer positions in PICMG technology subcommittees, including COM Express since its inception in 2004.

Christof Reuger, Advantech: Christof Reuger is Advantech's representative to the COM Express R2.1 subcommittee.

For more information about the COM Express Revision 2.1, contact Jeff Munch at