Industry Standard Architecture
Industry Standard Architecture (ISA) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088-based IBM PC, including the IBM PC/XT as well as IBM PC compatibles.
One 8-bit and five 16-bit ISA slots on a motherboard
8-bit XT, 16-bit ISA, EISA (top to bottom)
8-bit XT: Adlib FM Sound card
16-bit ISA: Madge 4/16 Mbps Token Ring NIC
In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components and software, including communication protocols.
Four PCI Express bus card slots (from top to second from bottom: ×4, ×16, ×1 and ×16), compared to a 32-bit conventional PCI bus card slot (very bottom)