COM Express hot among military electronics users while CompactPCI levels off

5PICMG standards such as CompactPCI have been leveraged for years in aerospace and defense applications such as communications, avionics, and satellites. Today, the fastest growing standard from the PICMG experts is COM Express, thanks to its flexibility and reduced size, weight, and power (SWaP) characteristics.

Standards such as , Advanced TCA, and – to some extent – have played a role in aerospace and defense electronics applications. CompactPCI led the way, as it provided a robust, cost-effective alternative to VME, especially in the 3U form factor. Today, however, stringent requirements are requiring form factors smaller than 3U; this area is where the standard is thriving.

“COM Express is very hot right now,” says Roy Keeler, senior product manager and manager of business development, aerospace and defense, ADLINK Technology (San Jose, California). “COM Express can be used in multiple military applications where reduced SWaP is a priority, such as unmanned aerial vehicles (UAVs), , and more.

“It is being used to operate subsystems, for instance. Mostly subsystems have a box with some I/O added to it and use Com Express as a controller,” he continues. “In areas where you don’t need high compute power, you can build a standalone solution that leverages a NVIDIA Jetson TX2, for instance. The enticing thing about Com Express is its flexibility when it comes to multiple pinouts and module sizes that are all available right off the shelf. It also has multiple display and video outputs with 16 lanes of PCIe 16 or two PCIe 8 outputs, which translates to a lot of I/O coming in a small package. You can also tailor the compute power based on SWaP requirements – from a Xeon to a Corei5.” (Figure 1.)

Figure 1: ADLINK’s Express-BD7 – a COM Express COM.0 R3.0 Basic Size Type 7 module supporting the 64-bit Intel Xeon processor D and Pentium D processor system-on-chip (SoC) – is specifically aimed at designers needing excellent computing performance with balanced power consumption and multiple 10G Ethernet connectivity in a long-product-life solution.

“COM Express is also a busless system, so you don’t need a backplane, which makes it attractive for customers who do not need the high-speed switched fabrics that come with a system,” Keeler notes. “It has the same processing power and no backplane.”

“From the Connect Tech perspective, we are seeing a significant interest in COM Express Type 7, the ability to leverage server-class processing power that was previously unavailable under the COM Express standard,” says Michele Kasza, vice president of sales at Connect Tech (Guelph, Ontario). “Access to Intel Xeon D processors and being able to hit scalable computing performance with access to four, eight, and 16 core processors, makes Type 7 an exciting new option. What was originally only available in large rackmount systems can now be accessed in small-form-factor solutions, ruggedized, and ready-to-deploy compute platforms. The other key feature is the introduction of high-bandwidth 10 Gigabit Ethernet (10GbE) network communication. Our customers can now make use of this high bandwidth connectivity using native Xeon D 10G capabilities.”

COM Express update added functionality

As Kasza mentions, the latest update to COM Express adds server-grade functionality to COM Express embedded computing systems. Revision 3.0 of COM Express provides for a new Type 7 connector and the addition of up to four 10GbE interfaces on the board, according to . According to the organization, previous revisions of the specification were limited to a single Gigabit Ethernet interface. The higher-speed ports open up new markets such as data centers, where the high compute density of COM Express can result in increased rack utilization. The 10GbE ports are also ideal for high-bandwidth video applications such as surveillance. Another change to the specification includes increasing the number of PCI Express lanes to 32 across the Type 7 connector, a move that provides a wealth of connectivity and interface options, including the ability to facilitate the use of general-purpose graphics processing units (GPGPUs). (Figure 2.)

Figure 2: Connect Tech has released an off-the-shelf COM Express Type-7 carrier board. This carrier occupies the same footprint as COM Express Basic at only 95 by 125 mm.

“It’s COM Express, number one,” says Mark Littlefield, head vertical product manager, defense, for . “While COM Express was not explicitly designed with rugged deployed military systems in mind, it has proven to be tremendously versatile and is allowing us to design and deploy smaller and less expensive systems than blade-based approaches could support. Type 6 COM Express is ideal for general solutions where the typical complement of I/O (USB, SATA, serial ports, audio, video, GPIO, etc.) is needed, while Type 7 swaps video and audio for 10GbE and more PCI Express ports for more demanding streaming I/O processing applications.”

COM Express growth is emblematic of the strength of the overall computer-on-module market.

“Computer-on-module market growth is just outstanding for certain types of form factors, and COM Express crosses both industrial and military lines. Curtiss-Wright uses it in a healthy number of systems, as we’ve found it to have significant advantages over PC/104 systems,” says Mike Southworth, a product marketing executive with Curtiss-Wright Defense Solutions (Ashburn, Virginia). “Historically, Parvus [acquired by Curtiss-Wright in 2013] mission computers were designed with PC/104 technology, which helped us achieve a great degree of modularity. However, PC/104 SBCs [single-board computers] didn’t have standardized I/O connectors like COM Express, and this led to longer engineering development cycles for system integration, which meant longer time to market. In addition, PC/104 introduced thermal management challenges when using hotter CPUs.

“When we started to integrate COM Express modules into our system architectures, we reduced our legacy system size by more than 25 percent, increased system technology re-use, and overcame our traditional thermal management challenges,” Southworth continues. “COM modules works quite well for reduced SWaP applications in avionics and other applications that require the smallest SWaP possible.” (Figure 3.)

Figure 3: Curtiss-Wright leverages COM Express for its ultra-small-form-factor (USFF) mission computer, the Parvus DuraCOR family.

ATCA and MicroTCA

Use of Advanced TCA and MicroTCA standards are declining within the defense market, according to many in the industry.

“ACTA and µTCA seem to both have fallen by the wayside,” Littlefield says. “I think that VPX has done a pretty good job at supplanting them within the defense market.”

“We see a little bit of and MicroTCA, but ATCA in military applications is declining according to a merchant embedded board market survey,” Keeler says. “The issue is that the form factor is too big for anything but wide-body type aircraft.”


The CompactPCI standard first became popular in 6U form factors with telecommunications applications, then as a cost-effective alternative to VME in military electronics applications, eventually becoming the choice standard in military 3U applications until the VPX standard was released. Today it has a strong legacy business, but not everyone agrees on its future growth within military applications.

“CompactPCI is still being used in military applications in the U.S., but it it’s not getting new designs as the industry continues to migrate to VPX,” Keeler says. “We still support a mix of 3U and 6U CompactPCI products military applications such as communication racks.”

“Curtiss-Wright consciously moved away from CompactPCI some number of years ago as 3U VPX began to rise and become the preferred choice among our military customers,” Southworth says. “We don’t see CompactPCI having a resurgence, rather only for legacy program support.”

Others are much more bullish on CompactPCI in defense applications: “CompactPCI is still a surprisingly strong seller, both within the U.S. and internationally,” Littlefield says. “As a result, we are continuing to refresh both our 3U and 6U product lines. (See Figure 4.) One may have thought that VPX would do the same to CompactPCI as it did to ATCA and µTCA, but that hasn’t been the case. CompactPCI continues to be an attractive solution, especially for systems that don’t have the huge backplane and out-of-box I/O requirements that VPX is more geared for – although there are customers out there that opt for the CompactPCI Serial route in order to leverage infrastructure, IP, and technical expertise gained from previous projects. We see at least a couple more generations of CompactPCI product in our future, and perhaps even more.”

Figure 4: Kontron offers the 6U CP6006(x)-SA, a Xeon-D-based SBC that is highly scalable (from two to 16 cores). For 3U, the CP3004-SA – a 5th-generation Core-i7 based SBC with a range of expansion options – is available.

CompactPCI Serial

CompactPCI Serial is PICMG’s serial answer to the VPX standard out of VITA. It has yet to gain much traction in U.S. defense applications, but interest is mounting and the new standard is gaining ground in Europe.

The core CompactPCI Serial specification provides high-speed serial performance to the 3U/6U Eurocard form factor, according to a PICMG release. It enables the use of PCI Express Gen3, 40GbE, or other high-speed protocols with a rugged and cost-effective connector solution. It is used in a wide range of applications, including railway/transportation, military/aerospace, industrial automation, and more.

Engineers at Elma Electronic (Fremont, California) have sold a CompactPCI Serial 3U solution to a defense customer for a significant upgrade of CompactPCI in a maritime application, says Steven Gudknecht, product marketing manager for Elma. In some cases CompactPCI Serial can be as much as 75 percent more affordable than VPX without a loss in performance, he adds.

“There are customers out there who are finding success with CompactPCI Serial – enough that we support them with new products,” says Mark Littlefield. “What we’re finding is that these customers all have a long legacy of working with CompactPCI, but their applications require them to make use of high-speed serial I/O. It only makes sense, then, to leverage all of the assets acquired through that legacy and adopt CompactPCI Serial rather than jump to an entirely new form factor like VPX.”

ADLINK has yet to see that kind of activity for military applications, Keeler says. “We not getting much uptake on it and have not put into a road map yet as there have not been a lot of inquiries for it.”

PICMG members recently ratified the CompactPCI Serial Space specification, which is a ruggedized version of CompactPCI Serial that specifically addresses the extreme environment requirements for outer space. The CPCI-S.1 R1.0 specification, ratified in August 2017, is intended for use aboard deployed satellites as the platform system and the payload controller; it can also be used on Earth for the control systems and ground stations. According to the spec, regular CompactPCI Serial products can be combined with CompactPCI Serial Space products to develop test and simulation systems.

CompactPCI Serial Space was selected for the OneWeb program, under which more than 900 satellites will use the technology to logically interlock with each other to create a high-speed connectivity coverage footprint over the entire planet.