XT bus architecture

from The Free On-line Dictionary of Computing (8 July 2008)

XT bus architecture

   <hardware, architecture> (After the {IBM PC XT}) 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 disc} controller

   (1997-09-15)