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 [IBM PC AT 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], used with permission.