Glossary for Geospatial Science

bus:The circuit channel or path a computer uses to move data and send signals between devices.  A microcomputer’s bus architecture determines what kinds of peripheral circuit cards can be plugged into its expansion slots.  DOS and OS/2 computers have four varieties of bus architecture: PC, AT (also called ISA), EISA, and Micro Channel.  The original PC bus handles 8-bit data.  The AT bus doubled the data width to 16 bits and became the industry standard (thus ISA, for Industry Standard Architecture).  IBM introduced the PS/2 with a proprietary bus, the 32-bit Micro Channel.  Other vendors countered with a 32-bit Extended ISA (the EISA).  The PC/ISA/EISA buses are backward compatible: that is, expansion cards designed for an older bus will normally work in a newer bus slot.  Thus, an 8-bit display board from a PC bus works in a 16-bit ISA slot or a 32-bit EISA slot, but a 16-bit display board for an ISA bus does not work in an 8-bit PC slot.