13.5
Silberschatz, Galvin and Gagne ©2009
Operating System Concepts – 8
th
Edition
I/O Hardware
Incredible variety of I/O devices
The control of devices connected to the computer is a major concern
of OS designers.
Common concepts : CPU
PORT
BUS
Controller
Port
Bus (daisy chain or shared direct access)
Controller (host adapter)
How can the processor command controller?
Controller has one or more registers for data and control signals.
The process communicates with the controller by reading and
writing bit patterns in the registers.
I/O instructions control devices