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Industry Standard Architecture Bus (ISA Bus)

Definition - What does Industry Standard Architecture Bus (ISA Bus) mean?

An Industry Standard Architecture bus (ISA bus) is a computer bus that allows additional expansion cards to be connected to a computer's motherboard. It is a standard bus architecture for IBM compatibles. Introduced in 1981, the ISA bus was designed to support the Intel 8088 microprocessor for IBM’s first-generation PC.

In the late 1990s the faster peripheral component interconnect (PCI). Soon afterwards, use of the ISA bus began to diminish, and most IBM motherboards were designed with PCI slots. Although there are still a few motherboards being made with ISA slots, these are generally referred to as the legacy bus motherboards.

Techopedia explains Industry Standard Architecture Bus (ISA Bus)

The ISA bus provides direct memory access using multiple expansion cards on a memory channel allowing separate interrupt request transactions for each card. Depending on the version, the ISA bus can support a network card, additional serial ports, a video card and other processors and architectures, including:

  • IBM PC with Intel 8088 microprocessor
  • IBM AT with Intel 80286 processor (1984)
  • Extended Industry Standard Architecture (1988)
The ISA bus first included synchronicity with the CPU clock. It was later upgraded to high-level buffering, which interfaced the chipsets with the CPU. Likewise, the ISA bus used bus mastering, which directly accessed just the first 16 MB of main memory.
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