Faster Storage and Networking Interfaces Boost Performance of COM Express and CompactPCI Serial-based Systems

Opening new applications for Transportation, Machine Control and Test.

The adoption of new storage form-factors, such as DOM, M.2 and U.2, which employ the wider use of non-volatile memory express (NVMe) architecture, are fueling new industrial applications. NVMe technology improves performance when building small systems that require large, fast local data storage.

Second, as system-on-module (SOM) solutions mature, next generation Ethernet interfaces are being offered as integrated Network Interface Controller (NIC) chips included within the SOM device. More full-featured computer-on-module (COM) solutions that use 10 Gb capable integral NIC devices are coming on line.

As companies including congatec and ADLINK roll out the COM Express Type 7 module (Figure 1), more capable small form-factor systems can now be built. New systems can now offer better, 10 Gbit Ethernet network interfaces as part of the COM Express module.

Figure 1: Typical COM Express Type 7 Module

Figure 1: Typical COM Express Type 7 Module

More Technological Advancements

Considering other system solutions that require pluggable or removable boards, advancement in follow-on Eurocard pluggable modules is demonstrated with new chips being offered on CompactPCI Serial modules, instead of the older parallel bus-based CompactPCI standard.

These standards are controlled by the PICMG organization, which makes them readily accessible to users for a small fee. As more suppliers come into the CompactPCI Serial space, better chip level solutions allow more functions to be placed on a 3U Eurocard.

A key differentiator with CompactPCI Serial, over the older CompactPCI, is that the new form-factor supports a high-speed module-to-backplane differential pair connector, allowing the user access to a standardized pluggable 3U module that can mate with a mid- to high-speed backplane.

Mechanical and Interface Design vs. Function

Considering the storage, network, and packaging needs, a quick look at form-factor, size, and electrical interfaces reveals:

  • Changes to the physical storage form-factor
  • Introduction of new physical network interfaces and connectors
  • Fanless designs being used with COM Express modules

Further, 3U CompactPCI Serial plug-in modules or boards employ serial fabric-based interfaces that now support low slot count, high performance, and lower-cost 3U board-based systems.

Figure 2: Storage Modules: M-SATA vs. M.2

Figure 2: Storage Modules: M-SATA vs. M.2


These devices are changing from the 2.5” and 1.8” solid state disk (SSD) form-factor to new choices developed for the laptop market. Over the last five years, Mini-PCIe and M-SATA have been introduced and used as new form-factors on COM Express carriers and various motherboards (Figure 2).

These edge card-based modules have been placed on COM Express carriers and within motherboards to expand I/O and provide storage solutions in a smaller space. More recently, M.2, and now U.2, SSDs have emerged that also use edge card connectors, but are offered in larger foot prints than Mini-PCIe or M-SATA modules.

These modules are offered with solid state storage capacities ranging from 128 MB to 2 TB. More interesting is the shift to the use of the NVMe storage interface. NVMe uses the PCIe electrical standard, resulting in much higher storage bandwidth.

Considering a one lane interface comprised of a send and receive pair, the older SATA 3 interface would allow 1.5, 3.0, or 6 Gb/sec transfers. NVMe with PCIe allows 2.5, 5, and 8 Gbaud transfers, providing 2.0, 4.0, and effectively just under 8 Gb/sec throughputs per lane.

With NVMe, devices can use one, four, eight, or more lanes that can scale the storage device interface bandwidth—allowing the physical connection to the SSD array to operate at GB/sec throughputs instead of MB/sec throughputs. To achieve higher rates, new SSD memory devices from Samsung, Intel, and Micron now allow SSDs to operate at two to four times the transfer rate of SSDs that formerly used the 6 Gb SATA 3 interface.

A similar trend is seen with NVMe-based 2.5” SSDs that now use the U.2 form-factor and allow similar performance increases.

Network Interfaces

The industry now supports the use of USB 3.0 and 10 Gb Ethernet on Type 6 and Type 7 COM Express modules, respectively. The Type 7 COM Express modules features two 10 Gb Ethernet interfaces. The use of these newer high-speed interfaces requires better board design and improved connectors to accommodate the higher data rates.

Figure 3:  Storage Module Carrier with 4 TB on CompactPCI Serial 3U Board

Figure 3: Storage Module Carrier with 4 TB on CompactPCI Serial 3U Board

Specifically, considering the most recent change to the COM Express specification, the module definition supports both 1 and 10 Gigabit Ethernet interfaces. Small servers can now be built using COM Express modules. Further, the new USB 3.0 and Ethernet interfaces enable applications that utilize high-resolution video formats, such as HD-SDI and H.265.

Broadwell DE class CPUs provide integral 10 Gb Ethernet interfaces, along with traditional 1 Gb network interfaces. Considering the speed, manufacturers must consider whether to offer copper-only interfaces or to add the option to provide fiber interfaces.

In either case, presenting high speed I/O to the outside world requires new connectors.

OnTime Networks is offering embedded routers that provide I/O through Ceelok Fas-T connectors to distribute 10GBASE-T Copper Interfaces. Likewise, Elma Electronic Inc. has moved to the Hercules Connector to bring out higher-speed signals in newer COM Express based small form-factor systems.

High-speed Connection

Looking at other advances from PICMG draws attention to adoption of the CompactPCI Serial form-factor. First introduced in 2011, the form-factor was more quickly adopted in Europe.

As new CPU and network devices are offered, there is a greater need to place these chips in front of higher-speed connectors to support the board-to-board connectivity. CompactPCI Serial does just that, using higher speed differential connectors on the module and the backplane. CompactPCI Serial allows industrial users of the older parallel-based CompactPCI standard to migrate to a serial fabric-based module and backplane scheme suited to industrial use at lower cost points that fit this market segment.

Typical applications include rail and transportation computer systems as well as machine control and now test instruments. For many, the draw to CompactPCI Serial has increased due to the use of standard Eurocard chassis with off-the-shelf backplanes, providing a pluggable and expandable modular system approach.

Manufacturers, such as Kontron, EKF, and MEN Micro, offer a wider variety of CompactPCI Serial boards to fit cost-sensitive, moderately rugged applications that can make use of the 3U Eurocard format (Figure 3). Standards-based packaging is available from existing manufacturers, with a choice of suppliers for the chassis and backplane solutions.

This can make implementation more straightforward with CompactPCI Serial vs. a COM Express solution, since standard packaging exists for CompactPCI Serial modules.

Compact Systems Enable High Data Throughput

New applications such as revised communication gateways and hyper-spectral image processing systems, as well as video analysis and presentation systems, can be realized by hosting them on small form-factors, or lower-cost, standard modular systems, such as CompactPCI Serial.

Network interfaces providing 10 Gb network connectivity allow the higher capacity data links necessary to support the transmission and processing of high-definition video, and handle aggregate data rates found in multi-sensor based systems.

New NVMe-based storage solutions align with higher-resolution sensors, and higher-performance CPUs, to support data capacity and the data rates emerging applications require.

The bits and pieces needed to implement smaller, faster embedded computing platforms continue to evolve, allowing developers to bring better platforms to market that host and enable exciting new embedded applications.

KenGrobKen Grob is Director of Embedded Technology, Elma Electronic. He holds a BSEE from Drexel University and has been in the embedded computing industry since 1985. The company manufactures electronic chassis platforms, embedded boards for storage, networking and processing, provides system architecture design, development, and implementation of complex solutions for communications, military/aerospace, medical and semiconductor equipment manufacturers.

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