Embedded trends: PC/104

PC/104 has been a workhorse of the embedded industry because of its small size, rugged construction, simple interface, PC software compatibility, and the huge array of off-the-shelf components available to developers. Unfortunately, the PC/104 architecture was originally based on the Industry Standard Bus (ISA) bus from the IBM personal computer. The name was derived from the PC and the number of interface pins on the 16-bit ISA bus. Since its introduction in 1992 by the PC/104 Consortium, designers have incorporated several enhancements into PC/104 to extend performance. Following the lead of the desktop, system architects added the PCI bus while retaining compatibility with scores of legacy ISA-based boards. The PCI bus brought a much higher data rate for high performance peripherals and application specific hardware. The specification for the PCI extension, formally known as PC/104-Plus, was released in 1997 and later updated in 2003. This specification gives board designers have the choice of incorporating the ISA bus alone, the PCI and ISA busses together, or the PCI bus alone. PC/104-Plus requires a new connector for the PCI bus pins and this loss of board space is one of the few disadvantages to the PCI upgrade. In spite of the lack of ISA silicon and a full ten years after the specification upgrade, PC/104 still outsells PC/104-Plus. Many designers feel that the lower cost and adequate performance makes the original PC/104 good enough for many applications. According to a recent study by Venture Development Corporation the market share of PC/104-Plus continues to grow and is expected to close to within about 6 percent by 2010. As the original PC/104 and PC1-4-Plus continue to deliver a superior platform for embedded products, can expect future communications extensions to include PCI Express and possibly USB.