Introduction of I/O and Problem

The Computer I/O Architecture is its interface to the outside world and a means of controlling and managing I/O activities. The I/O system consists of I/O devices, device controllers (or I/O modules or I/O interviews) and driver software.

There a various input and output problems and they include;

•Wide variety of peripherals.
  Delivering different amounts of data
  Running at different speed
  Running in a different format
•All devices are slower than CPU and RAM
• They need I/O modules
  -Interface to CPU and Memory
  -Interface to one or more peripherals
• The encoding of the transmitted word must be that which is employed by the I/O device.

• Operating Rates
  -The CPU and Main Memory operate at many times the speed of I/O devices
• Timing and Control
 -Exchange of status signals between CPU and device.
 -Rate of transmission from device to CPU or vice-versa.
• Communication Link (Word Length)
– There are at least 25 different word lengths used in computers. The word lengths vary from 4 to 128 bits.The separation (or combination) of words (because of word length) into characters, bytes or other units presents a "word assembly" problem.CA - XVII - I/O - 5WORD-LENGTH DIFFER