ARMed and ready

3ARM processors have traditionally been used as cores in intelligent peripherals. They are finally starting to show up on traditional single board computers (SBCs) as either the primary processor or in an FPGA with an integrated ARM core. Size, weight, and power (SWaP) criteria have driven choices in the past but what other factors are now being considered when choosing a processor?

VMEbus, introduced in 1981, was architecturally based on the Motorola 68000 processor bus and, as a result, all of the processor boards of those early days used 68000 processors. Over time, other processors were used, including Intel x86 and Sun Microsystems SPARC. Even Motorola moved on with the introduction of the 88000 RISC and PowerPC architecture processors. VMEbus has since morphed into VPX, a switched fabric architecture that is processor agnostic.

Today the processor of choice is usually something from the Intel family, often the 4th generation Intel Core processor family series. Intelligent peripheral chips that are ARM-based have been around for several years, and are widely used in computing platforms. Over the past 2-3 years, we at VITA Technologies have started to notice critical embedded and intelligent computing products, in particular SBCs and computers-on-modules (COMs) with host processors that are ARM-based. In our annual Business Barometer feature in this past Winter issue, we made note of this change as early as 2013, but in 2014, ARM finally made a strong showing. Today there are a number of suppliers using ARM processors with products in multiple form factors, mostly small form factor sizes.

ARM roadmap

ARM processors come in many configurations from many licensees. The ARM Cortex architecture is available in three series – A, R, and M, each targeted at specific applications (see Table 1).

Table 1: ARM processor series.
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Figure 1: ARM Cortex processor roadmap. Courtesy of ARM, 2H 2014, Expiration Q1 2015.
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Nearly every processor supplier has ARM-based processor families in their product lineup (see Table 2). Each has added their own special features and interfaces to the ARM core to differentiate their products. Application-specific processors based on ARM cores present a whole new wealth of choices for board developers, as many of the higher performance alternatives are excellent candidates for critical embedded computing platforms. Even FPGA suppliers have ARM core options available. ARM supports this FPGA strategy by developing processors for FPGA fabrics, enabling users to rapidly reach markets while maintaining compatibility with traditional ARM devices. The fabric independent nature of these processors enables board developers to choose the target device that is right for their application rather than be locked to a specific semiconductor vendor or architecture.

Table 2: Sampling of ARM technology-based solutions.
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Why ARM processors

Many designers choose an ARM processor to address one or more of the SWaP parameters that challenge their design (see Figure 1). ARM processors are recognized as being very power efficient while still delivering on performance, especially 64-bit, multi-core processors. But what other influences lead one to choose an ARM processor? VITA Technologies asked embedded computer vendors why they chose an ARM processor and what they see in store for their ARM-based products.

Dirk Finstel, CEO EMEA and Executive Vice President of the Global Module Computer Product Segment at LiPPERT ADLINK Technology GmbH pointed out three reasons why an ARM processor is attractive to their designers.

  1. As x86 processors haven’t been available in a range below 1-2 W TDP (thermal design point), ARM processors are the best fit to offer the best computing performance and lowest power consumption. As an entry-level product offering to build mobile embedded devices offering a rich I/O set, ARM cores are a mandatory requirement for our customers.
  2. As the majority of future embedded devices will be battery powered and connected to the Internet, with modest computing performance, ADLINK wants to be part of this Internet of Things (IoT) ecosystem offering those products. The low power needs of the ARM architecture makes this possible.
  3. Our customers coming from microcontrollers and low performance ARM devices are looking for higher performance, more memory, and high-speed I/O interfaces such as USB 2.0, PCIe, SATA, and LCD display cores. As most of them don’t have experience using complex operating systems like Windows Embedded Compact 7, VxWorks, or Linux, this opens a new market for ADLINK in which we haven’t participated in previously.

ADLINK primarily implements the Cortex-A series using a variety of processor cores tuned to the specific needs of the product lines. Entry-level products up to about 600 MHz use Cortex A8, moving to the Cortex A9 to get a performance boost up to 1.2 GHz, and single to quad cores. The Cortex A15 boosts that another 40 percent. The highest-end products benefit from the larger memory addressing capability of the Cortex A57 64-bit ARM processor.

ADLINK’s strategy is to use the Cortex M-series processors in co-processor controller roles for board management where they can act as control units for the primary processors to manage power sequence control, data acquisition units to gather temperature and voltage information, mean-time between failure (MTBF) real-time calculations, and forensic analysis.

Products that operate on batteries and have high computing performance needs will stick with the Cortex A-series processors. Intelligent peripherals with ARM cores embedded in FPGAs will be used for security cards as they offer the best performance at low gate counts and with a rich software ecosystem. ADLINK develops products over a very large spectrum of computing platforms, including COMs and handheld and tablet products where the performance of the Cortex A-series make a perfect fit.

Curtiss-Wright has made recent announcements of products that use ARM processors. Gregory Sikkens, Product Marketing Manager for ARM SBCs at Curtiss-Wright mentioned that they use the Freescale i.MX6, which has dual ARM Cortex A9 cores. “The device’s high degree of I/O integration, low power, low cost, and suitable performance make it very attractive for upgrades thanks to the flexibility of Freescale’s family of pin-compatible ARM devices,” stated Sikkens. “It enables easy upgrade to a quad core device for those applications and customers who prefer more cores.” The Freescale i.MX6 is used in the Curtiss-Wright Digital Beachhead Ethernet Switch and Vehicle Management Computer which is used in VICTORY “appliance” type applications.

Used in single board computer products is the Freescale Layerscape LS1020A, which is a dual ARM Cortex A7 core processor. Sikkens likes this processor because “This device is part of the QorIQ family that includes some of the Power Architecture devices that are used on our other SBCs, which provides a range of devices that share a familiar complement of I/O and features such as the Freescale security engine.” One key feature that is important to his customer base is that Freescale has ECC/parity across all the device’s memory and memory interfaces, including the cache; this is a Freescale enhancement that is not an available feature of the ARM core. Another reason is the availability of the device – it offered the earliest scheduled release with the right mix of features and performance to provide an ARM-based SBC that is I/O and pin compatible to existing Curtiss-Wright Power Architecture and Intel SBCs, while providing an upgrade path to higher performance devices as they become available.

The Curtiss-Wright first generation strategy for ARM processors is to use Freescale’s QorIQ Cortex devices mainly as the primary processor on rugged single board computers designed for use in demanding applications such as mission computers. They will also use the i.MX6 type of processors, which are ideal for use in “appliance” type applications as part of a complete system solution where a feature-rich I/O subsystem is required.

“We are seeing interest in the VPX3-1701 3U ARM-based SBC hosting a graphics mezzanine, such as our XMC-715 module, which enables us to provide a complete single slot graphics solution at less than 30 watts maximum power,” says Sikkens (see Figure 2).

Figure 2: The VPX3-1701 is the first release in Curtiss-Wright’s ARM SBC product roadmap.
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The reasons for implementing an ARM processor are widely varied. Besides the need to improve SWaP metrics for which ARM is exceptional, there are other reasons. The fact that there are hundreds of ARM licensees means that all types of application-specific components with very diverse I/O and features are on the market. New application-specific capabilities are being added constantly. This means that an SBC designer has many more choices, more appropriate than ever before to a specific application. The choice of the right ARM processors can help differentiate products in a very competitive SBC market.

Table 3: Sample of ARM-based suppliers.
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A search of the VITA product directory turns up several ARM processor-based products (see Table 3). The list continues to grow quickly as new products are introduced each month. The list is not at all inclusive – you can be sure there are many more products on the shelf today that are “ARMed and ready.”