XT bus architecture

The XT bus architecture is an eight-bit ISA bus architecture used by Intel 8086 and Intel 8088 systems in the IBM PC and IBM PC XT in the 1980s. It predates the 16-bit ISA architecture used on the Intel 80286 based machines.

The XT bus has four DMA channels, of which three are brought out to the expansion slots. Of these three, two are normally allocated to machine functions:

DMA channel  Expansion	 Standard function

0	      No	 {dynamic RAM} refresh

1	      Yes	 add-on cards

2	      Yes	 {floppy disk} controller

3	      Yes	 {hard disk} controller

See also:

• Extended Industry Standard Architecture

• Industry Standard Architecture

• Micro Channel Architecture

• Peripheral Component Interconnect

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Article based on XT bus architecture at FOLDOC.