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Low-Power CPUs

A Call to ARMs: Auto Industry Quality Standards Provide Path to SWaP-C Reduction

For a whole new emerging class of rugged and mobile systems where power, heat and compact size are critical considerations, the ARM architecture offers a wide range of flexibility for use in SoCs that can meet the tough demands of such applications.

DAVID JEDYNAK, CURTISS-WRIGHT CONTROLS ELECTRONIC SYSTEMS

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Size, Weight, Power and Cost are always concerns in rugged and mobile applications. However, the level of emphasis varies dramatically between the types of applications. In the ground vehicle market, applications range from highly armored tracked vehicles, such as Abrams or Bradley, to highly flexible and mobile tactical wheeled vehicles, such as the HMMWV and coming Joint Light Tactical Vehicle (JLTV). This applies as well to rugged civilian applications such as vehicles used in oil exploration and heavy industrial applications. Vehicle electronics and the required core processing is not a one-size-fits-all approach—what works for a tank is not necessarily what works for a truck. With regard to processing and vehicle electronics, a close look needs to be given to the automotive industry and how it is solving the challenge of bringing more and more electronics into the vehicle.

The demand for navigation, situational awareness, new radio technologies and media storage/playback has helped drive the success of ARM-based processors in the automotive market. Ranging from “bolt-on” aftermarket dash-top portable navigation devices, back-up cameras, satellite radio receivers, Bluetooth integration kits, 3G wireless hotspots and portable media playback (e.g. iPod) to factory installed built-in “Infotainment” systems such as the Microsoft Sync system in Ford Vehicles, low-power ARM-based processors are a vital enabling technology. Despite a limited 12-volt power system, no specialized in-cabin electronics cooling systems, and limited space and weight allocations for electronics (driven by both comfort based industrial design and technical performance such as fuel economy), automotive vehicle electronics designers are able to design high-performance systems around ARM-based cores at reasonable cost.

In heavy military vehicles, Intel processors and Power PC processors—often no different from desktop or laptop processors found in PCs or Macs—are the standard. Although of some importance in laptops, power consumption in desktop and servers has been of low importance compared to raw processing power. Operating in generally climate-controlled environments (0-55°C consumer environments), little optimization for environmental conditions and constrained SWaP-C has been performed. Just as in the automotive as well as mobile device markets, these types of processors have not provided a path to SWaP-C optimization in Light Tactical Vehicle space, often overburdening both crew and vehicle in terms of such things as suspension, power and fuel efficiency.   

In contrast, ARM-based processors are focused on SWaP-C constraints, enabling the vast majority of mobile devices—phones, media players, cameras, handheld game systems—as well as automotive-specific electronics like navigation devices, media playback and infotainment. ARM is a licensed core, not a complete processor such as is traditionally provided by Intel. In the traditional model, a complete processor is placed on a motherboard along with supporting chipsets (Northbridge & Southbridge) for memory access, video, USB/serial, audio and peripheral buses, such as PCI/PCIe, to create a complete system. ARM is different, as it provides a processor core that silicon manufacturers can license to use as the basis for creating purpose-specific System-on-Chip (SoC) devices. These SoCs integrate many of the traditional chipset features along with application-specific intellectual property blocks into a single die, allowing a tightly integrated SWaP-C optimized product. An example of this was fabless startup Centrality, acquired by SiRF Technology, which created ARM-based SoCs designed specifically for the portable GPS device market, integrating core technologies required for that product space, enabling product designers a highly integrated and cost-effective platform upon which to build products with minimal NRE and design time. Another example is Apple’s iPhone. Now being used in demanding military environments in Iraq and Afghanistan, the iPhone is an ARM-based design with lineage back to the first iPod developed with low-end ARM cores. Apple’s latest ARM-based design is the iPad, integrating an Apple-designed ARM-based SoC running at 1 GHz. Mobile handsets built around Google’s Android Operating System (Linux plus middleware) running on ARM-based SoCs have now surpassed the iPhone in market share after Q1 2010 according to NPD.

To address the growing interest in low-power optimized processors, Intel has recently launched the Atom chipset. The combination of high performance and low power provided by the Atom has helped drive the great growth of the low-cost Netbook market, in which a number of ARM-based designs also compete. Although not a complete SoC as it is still a two-chip solution (processor and Southbridge), the Atom represents a significant move by Intel toward the ARM-dominated market. More recently, in May 2010, Intel released a new generation of Atom processors, designed with decreased power requirements to target the ARM dominated mobile phone market. Freescale, maker of PowerPC processors common in the Military market, also offers a family of ARM-based SoCs focused on automotive, portable, industrial and medical markets. Freescale’s iMX31 ARM-based SoC is the heart of the Microsoft/Ford Sync system in automobiles, providing rich multimedia experiences with both voice recognition and voice synthesis, as well as navigation, vehicle health monitoring and emergency post-crash 911 calling services. A comparison of the power consumption of this class of devices with popular PC/server processors is shown in Figure 1.

Figure 1
A comparison of the power consumption of popular desktop/server processors with the recent low-power offerings in terms of watts from both Intel and ARM shows a significant advantage of the latter for low-power, rugged applications.

The growing availability of ARM-based SoCs provides a new opportunity for rugged and mobile system designers. A challenge is to ensure that ARM-based SoCs can meet certain specification ratings appropriate for use in the harsh environments found in these applications. The good news is that ARM-based SoCs are already qualified for harsh environments using the certification ratings developed by the Automotive Electronics Council’s (AEC) Component Technical Committee. In the past, the automotive industry had employed semiconductor MIL standards to identify suitable components for use in demanding automotive environments, but when the MIL standards were retired, the automotive industry collaborated to establish a replacement set of standards. Similar to MIL-STDs, the AEC standards provide common sets of qualification and testing levels for components, providing product and system designers assurance in environmental design.  

The AEC-Q100, Q101 and Q200 standards provide stress test qualification for ICs, discrete semiconductors and passive components, with multiple grades. At the highest level (Grade 0, generally intended for engine compartment), temperatures range from -40° to +150°C.  At Grade 3, the range is -40° to +85°C, temperatures experienced in the passenger compartment. The Freescale iMX31 ARM-based SoC in the Microsoft/Ford Sync system is an example of an AEC-Q100 Grade 3 component, as it needs to function reliably in a vehicle cold-soaked at 4 AM in a Maine winter and hot-soaked at 1 PM in an Arizona summer, as well as in post-crash situations for emergency services calling.  The AEC standards leverage existing Military testing standards (e.g. MIL-STD-883) as well as industrial standards (JEDEC, EIA, UL) including JESD89 for radiation-induced soft errors in integrated circuits. The automotive industry uses stringent reliability standards because, while they don’t see the extreme ballistic shock and tracked vehicle vibration conditions of heavy vehicle military applications, they do endure the wide performance temperature ranges and rough conditions of the automotive environment. The auto industry is providing a crucible to drive ARM-based SoCs to highest quality with low failure rates. On top of safety concerns, every customer service event in the auto industry eats into profits, driving a financial need for high reliability. 

At the higher end of processing requirements, applications such as sensor fusion and data fusion demand significant processor capability. These applications frequently use software developed under Windows or Linux, and will continue to demand the highest performance desktop/server processors available from Intel and Freescale’s PowerPC products. For the other classes of applications, such as Smart Displays, network devices and wearable computers, designing with low-power ARM-based SoCs could be ideal for SWaP-C optimization. The use of ARM cores in rugged and mobile applications should be explored for use not just in traditional microcontroller applications (motor controllers, etc.), but as processors employed for specific highly optimized uses, much like it is used in consumer, industrial and automotive markets. In addition to commonly used Real-Time Operating Systems for rugged and mobile applications, the increasingly popular Linux operating systems is very common on ARM-SoCs, and has in fact been a significant driver in the popularity of ARM for rapid product development in the consumer and automotive environments. Applications developed in Linux for Intel and PowerPC architectures can move to lower-power ARM-based SoCs with often no changes except recompilation into an ARM-compatible binary.

High-performance desktop/server processors require advanced cooling approaches such as conduction cooling, forced air, cold plate or liquid. These cooling provisions, along with larger power supplies, result in significant weight and size penalties to light tactical vehicles, which can’t always afford the power dissipation and price associated with these larger, high-end computing devices. Low-power processors, such as automotive AEC-Q100 qualified ARM-based SoCs, can provide a significant path to SWaP-C optimization. Lower power reduces the need for large power supplies and associated cooling methods, providing significant advantages in size, weight and power, as well as associated costs. Given the similarities between the automotive market and the light tactical vehicle market, leveraging the adjacent industry experience and qualification of these low-power processors is viable.  The time is right to start looking at this new generation of smaller, low-power devices and how they can drive a whole new class of rugged and mobile applications.  

SiRF Technology
San Jose, CA.
(408) 467-0410.
[www.sirf.com].

 

Curtiss-Wright Controls

Electronic Systems
Santa Clarita, CA.
(661) 257-4430.
[www.cwcembedded.com].