Single Board Computes

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Single-board computers (SBCs) are complete computers built on a single circuit board. The design is centered on a single or dual microprocessor with RAM, IO and all other features needed to be a functional computer on the one board. The first true single-board computer (see the May 1976 issue of Radio-Electronics) called the "dyna-micro" was based on the Intel C8080A, and also used Intel's first EPROM, the C1702A. The dyna-micro was re-branded by E&L Instruments of Derby, CT in 1976 as the "MMD-1" (Mini-Micro Designer 1) and was made famous as the example microcomputer in the very popular 8080 "BugBook" series of the time. SBCs also figured heavily in the early history of home computers, for example in the Acorn Electron and the BBC Micro. Other typical early single board computers were often shipped without enclosure, which had to be added by the owner, examples are the Ferguson Big Board and the Nascom.

With the development of PCs there was a sharp shift away from SBC, with computers being constructed from a motherboard, with functions like serial ports, disk drive controller and graphics being provided on daughterboards. The recent availability of advanced chip sets providing most of the I/O features as embedded components allows motherboard manufacturers to offer motherboards with I/O traditionally provided by daughterboards. Most PC motherboards now offer on-board support for disk drives including IDE and SATA with RAID, graphics, Ethernet, and traditional I/O such as serial and parallel ports, USB, and keyboard/mouse support. Plug-in cards are now more commonly high performance graphics cards (really graphic co-processors), high end RAID controllers, and specialized I/O cards such as data acquisition and DSP (Digital Signal Processor) boards

Applications

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Single Board Computers are now commonly defined across two distinct architectures: no slots and slot support.

Embedded Single Board Computers are boards providing all the required I/O with no provision for plug-in cards. Applications are typically gaming (slot machines, video poker), kiosk, and machine control. Embedded Single Board Computers are much smaller than ATX motherboards, and provide an I/O mix more targeted to an industrial application such as on-board digital and analog I/O, on-board bootable flash so no hard drive is required, no on-board video, etc.

The term "Single Board Computer" now generally applies to an architecture where the Single Board Computer is plugged into a backplane to provide for I/O cards. In the case of PC104, the bus is not a backplane in the traditional sense but is a series of pin connectors allowing I/O boards to be stacked.

Single board computers are most commonly used in industrial situations where they are used in rackmount format for process control or embedded within other devices to provide control and interfacing. Because of the very high levels of integration, reduced component counts and reduced connector counts, SBCs are often smaller, lighter, more power efficient and more reliable than comparable multi-board computers.

The primary advantage of ATX motherboards versus Single Board Computers is cost. Motherboards are manufactured by the millions for the consumer and office markets allowing tremendous economies of scale. Single Board Computers, on the other hand, are in a specialized market niche and are manufactured in much smaller numbers with the resultant higher cost. Motherboards and Single Board Computers now offer similar levels of feature integration meaning that a motherboard failure in either standard will require equivalent replacement.

The primary advantage of a PICMG Single Board Computer is the availability of backplanes offering virtually any slot configuration including legacy ISA support. Motherboards tend to the latest slot technology such that PCI slots are becoming legacy support with PCI-Express becoming the standard. In addition, motherboards offer, at most, 7 slots while backplanes can offer up to 20 slots. In a backplane 12.3" wide, similar in size to an ATX motherboard at 12", a backplane with a Single Board Computer can offer 12 slots for I/O cards with virtually any mix of slot types.