XT bus architecture

XT bus architecture

(hardware, architecture)(After the IBM PC XT) An eight-bitISA bus architecture used by Intel 8086 and Intel 8088systems in the IBM PC and IBM PC XT in the 1980s. Itpredates the 16-bit ISA architecture used on the Intel 80286based machines.

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

DMA channel Expansion Standard function0 No dynamic RAM refresh1 Yes add-on cards2 Yes floppy disk controller3 Yes hard disc controller