Buses are data connections between computers and internal or external devices. Bus adapters connect peripherals to computers that do not provide native support for a peripheral’s interface. For example, bus adapters enable communication between video cards and computer processors that do not share the same protocol. Some bus adapters are housed in cables that connect one bus to another. Others are board-level cards, blades, or stand-alone units with interfaces and power supplies. With hot swappable bus adapters, components can be added or removed without interrupting the operation of the main unit.
Bus adapters vary according to protocol or connective technology. Integrated drive electronics (IDE) is a standard electronic interface used between a computer motherboard’s bus and the computer’s disk storage devices. In 1990 the American National Standards Institute (ANSI) adopted the 16-bit IDE standard as the Advanced Technology Attachment (ATA). Another 16-bit standard, Industry Standard Architecture (ISA), can transfer data at a clock speed of 8 MHz and is capable of handling memory under 16 MB. Extended ISA (EISA) also runs at 8 MHz, but is capable of 32-bit data transfers and can access all system memory.
Another common bus, the general purpose interface bus (GPIB), is designed to connect computers, peripherals, and laboratory instruments so that data and control information can pass between them. Bus adapters for research 1394, a universal serial bus (USB), provide high-speed connections to components such as hard disks, CD-ROMs, DVDs, graphics cards, and monitors. VersaModule Eurocard (VME) is a 32-bit bus used in industrial, commercial, and military applications. VME Subsystem Bus (VSB), an auxiliary bus used with VMEs, helps speed data transfers between devices.