The saying “less is more” sums up why many embedded designers are usingmini-ITX boards in space-constrained systems ” by offering greaterflexibility and long-life support, these ultra-compact motherboards aredelivering much more value than standard motherboards. Systemdevelopers are taking advantage of boards with more expandability,graphics and CPU options, making them better suited to serve a broadrange of embedded applications.
Measuring 170 mm (6.7 inches) per side, mini-ITX is just 38% the sizeof the mainstream ATX boards, which makes it one of the smallest PCform factors. Designers achieve this density by focusing on thermalmanagement and the careful selection and placement of board components.They model airflow and cooling solutions ” heatsinks and fansinks ” toensure the temperatures of all board components are maintained withinfunctional limits.
Mini-ITX adoption is growing in many embedded market segments, suchas medical, test and measurement, transaction terminal and gaming.These applications benefit from the PC ecosystem that provides a widechoice of vendors for hardware components and software, with theadvantage of competitive pricing and interoperability.
Venture Development Corporation (VDC) estimates the mini-ITX marketwill nearly double between 2005 and 2008, from $22M to $41Mrespectively. The CAGR is expected to top 20 percent, which issubstantially greater than the growth forecast for other form factors,as shown in Figure 1 below.
|Figure1. Compound Annual Growth Rate (CAGR) By Form Factor|
Why Not Go With a Standard PC Board?
Although standard motherboards support the majority of thefunctionality needed by many embedded applications, they fall short onthe requirements for some applications. Two universal reasons forchoosing mini-ITX are the space and thermal constraints of manyembedded systems. They require small boards with low power consumptionthat function properly despite little airflow. The environment in whichthese boards operate also impacts the choice of CPU and system memory,especially if the boards must be fanless.
The CPU power consumption contribution can be seen when using amini-ITX board, equipped with one of four processors, as shown in Figure 2 below. The chart shows thepower consumption for different processor loads for the entiremotherboard, including one gigabyte of DDR2 memory, processor andfansink (the ULV Celeron M 423 is passively cooled with a heatsink andno fan).
The two Intel Celeron M processors maintain relatively flat powerconsumption of about 20 watts. Under heavy loading, the Intel Core Duoprocessor peaks around 30 watts, and the Intel Core 2 Duo reaches justover 50 watts. All four of these configurations have substantiallylower power consumption than most commercial PC boards based on desktopchipsets.
|Figure2. Mini-ITX Board Power Consumption|
Another reason many embedded applications forgo mainstream PCmotherboards is the need for easier access to board functionality.Unlike consumers, embedded system engineers regularly take advantage ofsystem functionality such as general purpose I/O (GPIO), mini-PCI slotsand TrustedPlatform Module (TPM) headers. Mini-ITX vendors make thesefeatures and others readily available, as shown in Figure 3 below.
They may also offer a different mix of peripherals than standardPCs, like including two or more Ethernet ports as opposed to a singleport. With two separate Gigabit Ethernet controllers, a mini-ITX boardis suitable as an intelligent gateway or server. Wireless support canalso be added via the mini-PCI socket so it can become an access point.
|Figure3. Mini-ITX Motherboard|
Many embedded market segments require long-life boards, especiallyif they must be certified to comply with government regulations orcustomer specifications. Embedded mini-ITX board vendors providerevision control and minimize manufacturing changes by usingextended-life components. Reliability is also increased through the useof high quality components.
Despite the board differences already highlighted, it's criticalthat mini-ITX boards perform just like a PC motherboard, flawlesslyrunning Windows XP, Vista or Linux and supporting standard peripheralsand interfaces.
The key mini-ITX differentiator compared to a standard ATX form factorboard is the size of the board. Despite the compact size, many mini-ITXboards are packed with I/O such as four serial ports, eight USB 2.0ports and dual Gigabit Ethernet ports. Multiple video interfaces – VGA,LVDS, TV-out, a x16 PCI Express slot for graphics acceleration cardsand Media Expansion cards – provide lots of flexibility for differenttypes of video solutions.
The one thing which mini-ITX boards do not have is lots of PCI andPCI Express expansion slots. However, there are still numerouspossibilities for adding expansion cards such as the x16 PCI Expressslot (also for use with x1 PCI Express cards), a mini-PCI socket, aCompactFlash socket and a PCMCIA socket.
The use of an Intel mobile chipset enables a choice of processors,ranging from an Ultra Low Voltage Celeron processor which can bepassively cooled to a mid range Core Duo or a high performance Core 2Duo processor. This offers system designers a lot of flexibility inselecting the right processor to suit their application's need in termsof price, performance and power consumption.
Board vendors may also offer a choice of fansinks and heatsinks foruse with these processors, enabling operation of the mini-ITX board inhigher temperature environments ranging from 60 ” 70 degree C ambientoperating temperature for the mini-ITX board as shown in Figure 4 below . The external temperatureoutside the chassis would typically be 10 degrees C lower than theinternal temperature, depending on the thermal design of the chassis.
|Figure4. Cooling Solutions|
Many embedded systems need display performance that goes beyond thecapabilities of graphics functionality that's integrated in moststandard PC chipsets. Medical imaging, kiosks and casino gamingapplications often deploy combinations of low and high resolutiondisplays. Video and graphics capabilities can be enhanced throughexpandability options that conform to the mini-ITX specification.
|Figure5. Ambient Operating Temperature|
One way this is done is to incorporate a PCI Express interface (e.g.x16) for high-end video or graphics cards. This interface may also beused for commercial off-the-shelf (COTS) Media Expansion Cards,formally known as ADD2+ cards that provide flexible digital display andvideo-in capabilities on a single add-in card.
High reliability, long-life Media Expansion Cards are available frommany board and card vendors and support a wide range of configurationsincluding dual digital video interface (DVI) or dual low voltagedifferential signaling (LVDS) video interfaces.
Although USB is one of the most convenient ports for connectingperipherals to desktop and laptop PCs, embedded systems may deployother end-user interfaces. Mini-ITX boards often support a range ofuser-level expandability by incorporating various sockets such asCompactFlash, PCMCIA Type II and Mini-PCI. They are used by photoprinting kiosks that read files from various media cards andpoint-of-sale terminals that identify restaurant staff through ID keyrings. This expansion capability can be applied to just about any kindof portable removable digital media, add-in card or networking card.
In addition to satisfying a common set of embedded requirements,mini-ITX vendors also support application-specific needs. This helpsaddress particular constraints and priorities around functionality,reliability and maintainability. The following discusses how mini-ITXmeets the needs of medical, test and measurement, transaction terminaland gaming systems.
Medical equipment used for clinical diagnostics, such as computedaxial tomography (CAT) scanners, is constantly evolving. Developersstrive to increase test accuracy and speed and simplify the machineinterface for health care professionals.
The wide-spread use of CAT scan, magnetic resonance (MR) andultrasound equipment is magnifying the importance of extending systemlifetime to increase ROI and maintaining careful revision control tosafeguard patient safety. As the number of systems grows, there's ahigh priority on low power to avoid overloading the facility's energydelivery infrastructure. System designers are also developing morecompact and quieter medical equipment to improve diagnostic roomergonomics.
Medical imaging applications require a high level of compute andgraphics performance. Many stations have two displays, one to renderthe medical image and the other for patient information. High-endsystems may require mini-ITX based-systems with dual display capabilityand a graphics add-in card. Systems that use low-end CPUs may runfanless, reducing noise and susceptibility to fan failure.
Test and measurement systems, such as logic analyzers andoscilloscopes, are durable and long lasting. As a result, these systemsdeliver many years of service to development and certification labs,making system turn-over relatively low. Manufacturing a large varietyof systems, each with fairly small volumes, test and measurementequipment makers are motivated to keep their designs in production aslong as possible.
This also helps to curtail their system testing requirements, asmany of these systems are certified for extended temperature, relativehumidity operation and enhanced shock and vibration. This marketsegment relies on long-life boards and revision control to containdevelopment and validation costs.
Some test and measurement systems also connect to one or moreexternal displays, so mini-ITX boards must support different monitoroptions. They must also keep up with the increasing performance of thedevices they are testing, so system developers are turning tomulti-core processors for a computing boost. Since these systems arecompact, low power is also a key requirement.
Information displays and transaction terminals are used to grabcustomers' attention and provide them service. Travelers enteringairports see large screen displays, check-in at ticketing machines andpay airline agents at point-of-sale terminals with cash registers.
These systems operate 24/7 and any downtime impacts business, sosystem developers pay careful attention to hardware and softwarereliability. System availability is further complicated by the use ofassorted peripherals like price scanners, touch screens and receiptprinters, which increases the need for thorough validation testing. Ifsoftware and interoperability issues crop up, board vendors may becalled in to help resolve the issues.
Transaction terminals and information displays often require passivecooling with mini-ITX boards mounted under keypads, monitors anddisplays. Some systems have dual displays, one for the cashier and theother for the customer. Since system boards are reused to supportdifferent store chains and multiple segments like retail, lottery andkiosk, they are typically designed into many systems over many years.
Las Vegas and many other gaming destinations experienced a rebirth afew years ago. Today, casinos are filled with high tech slot machinesthat play a wide assortment of games and are equipped with brilliantdisplays. They must operate 24/7 and remain secure. This often requiresadditional security requirements, such as write-protected, socketedBIOS. These features help prevent hackers from modifying the system andallow the casino to pull the BIOS chip and check whether it wasmodified.
Gaming systems are typically certified in multiple U.S. states andcountries across the globe, which is very expensive. Board changes andrevisions force gaming machine manufacturers to recertify theirsystems, making long-life boards crucial to profitability.
New Requirements For Mini-ITX?
Continuously evolving embedded systems with new requirements test theflexibility of mini-ITX boards. Medical imaging systems, storing largeamounts of patient data, will demand more reliable and secure storagesystems.
Transaction terminals, connected to the Internet, must keep up withadvances in security software. Test and measurements systems need to beas fast as what they're measuring, so they need ever-increasingperformance. And gaming systems must be protected against hackers byusing the latest, secure operating systems and device drivers.
Although mini-ITX is engineered for embedded use, it is based on PCarchitecture which serves applications with the same issues. With thewide deployment of PC systems, new solutions are being developed everyday, which also benefits mini-ITX users.
Peter Mitchell is the Sr. Product Line Manager for EnduraMotherboards at Radisys. Peterhas been with RadiSys since 1999 and has managed the introduction andlifecycle of eight generations of embedded motherboards. He has an MBAfrom Wolverhampton University, UK and a Ph.D from Cambridge University,UK.