System Fundamental Week 8 - CameronProvost/Tech-Journal GitHub Wiki

Difference between Serial and Parallel Transmission

In serial transmission 8 bits are transferred at a time, having one starting bit and one stopping bit. One bit is transferred at each clock cycle.

Parallel transmission is generally used for short distance, many bits are transferred simultaneously. 8 bits travel each clock cycle.

I/O Control Methods

There are 5 I/O control methods that allow I/O devices to connect and communicate with the system; these include programmed I/O (Links to an external site.), interrupt-driven I/O (Links to an external site.), memory-mapped I/O (Links to an external site.), direct memory access (Links to an external site.), and channel-attached I/O (Links to an external site.).

Programed I/O

This is the simplest where the CPU continually monitors a poll associated with the I/O port.

Interrupt Driven I/O

This is the opposite of the Progamed method. Instead of the CPU asking for signals from the devices when there is activity the devices tell the CPU they have activity.

Memory Mapped I/O

This method gives each I/O device its own block of memory. Thus this method looks just like memory access from the point of view of the CPU.

Channel I/O

With Channel I/O one or more I/O devices are given a pathway called a channel path. This method is for slower devices where their management can be combined through only one controller.

Character I/O vs Block I/O

Characters wait in a buffer until the scan code reads that a key has been pressed. Charter I/O deals with keyboards. Block I/O deals with magnetic disks and tapes. These are managed in I/O blocks where the block sizes differ depending on the software and applications involved.