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
IBM Personal Computer AT
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The IBM Personal Computer AT was released in 1984 as the fourth model in the IBM Personal Computer line, following the IBM PC/XT and its IBM Portable PC variant. It was designed around the Intel 80286 microprocessor.
IBM 5170 with Floor Standing Enclosure and compatible non-IBM display