Applications
Single board computers are now commonly defined across two distinct architectures: no slots and slot support.
Embedded SBCs are units 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 SBCs are much smaller than the ATX-type motherboard found in PCs, 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 memory (eliminating the need for a disk drive), no 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 an ATX motherboard as compared to an SBC 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 SBCs 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.
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