Single Board Computers
Single board computers (SBCs) are functional computers built on a single circuit board including microprocessor, memory, input/output (I/O) and other required features. Unlike desktop personal computers, sbc’s typically operate without requiring expansion slots for peripheral functions and are optimized for smaller form factors. Single board computers use a wide variety of processors with designs ranging from high performance servers in compact space-saving formats to low power modules as small as a pack of gum.
SBC’s provide advantages in a variety of applications, due to form factor, weight, cost, reliability and environmental ruggedness. SBCs are commonly used within industrial situations as rack mount computers for process control or embedded within other devices to provide control, analytical data, and user interface. Because of the very high levels of integration, reduced component counts and reduced connector counts, single board computers are often smaller, lighter, more power efficient and more reliable than comparable multi-board computers. These advantages make SBCs popular in medical instruments, transportation systems, military/aerospace, industrial controls and countless other high reliability applications.
Driven by the increasing density of integrated circuits and system on chip (SOC) processors, sbc’s are incorporating more processing power and/or more input/output (I/O) capability into smaller and smaller form factors. There are several industry standard form factors for SBCs as well as proprietary and custom form factors for specific applications. Some form factors are completely standalone; some include stackable or modular expansion, and others offer expansion through backplanes or mezzanine boards.
One common variety of sbc uses standardized form factors intended for use in a backplane enclosure. Some of these types are STD Bus, CompactPCI, PXI, VMEbus, VXI, and PICMG. The intelligence and interface/control circuitry is often placed on a plug-in single board computer that is then inserted into a passive (or active) backplane. Backplanes are available with a mix of slots (STD Bus, ISA, PCI, PCIX, PCI-Express, etc.) and can range from small 2 slot varieties with many options available for to fit in a 19″ rackmount enclosures.
Another popular format for single board computers are the ITX platforms. Originally defined by VIA Technologies with the Mini-ITX (Information Technology eXtended) reference design, these industry standard form factors have been heavily adopted by SBC embedded computer manufacturers. As true sbc’s, they are fully functional as stand-alone SBCs, though they can offer expansion options. Currently there are four ITX standard form factors, including Mini-ITX (170mm x 170mm), Nano-ITX (120mm x 120mm), Pico-ITX (100mm x 72mm), and Mobile-ITX (75mm x 45mm).
Some rugged sbc form factors have connectors which allow expansion hardware and power supplies to be added. These industrial SBCs often feature locking connectors, thicker PCBs and designs for extended temperature operation. The PC/104 Consortium is one organization that publishes specifications for these industrial single board computers. Their single board computer standards include PC/104, PC/104-Plus, PCI-104, PCIe/104, PCI/104-Express, EPIC, EPIC-Express, EBX, and EBX-Express.
With the variety of I/O available, processors and board form factors, single board computer design engineers have a tremendous number of tools at their disposal to design a system that meets customer’s very stringent and specific specifications. The usage of single board computers will continue to explode as the need to collect, analyze and share data increases in environments where multi-board computing simply cannot affordably survive.
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