Computer Organization and Architecture

Presented By:

Vikram Patel

Topics

Input Output (I/O) ports

Input Output Mapping

Memory map techniques

Interrupt driven I/O

DMA based Input Output

Input Output Processor

Input-Output ports ( I/O Ports)

Input : Information or data to the computer

Output : Information or data from computer

Computers are based on the fundamental idea that every input results in an

output.

What is Input and Output ?

What are Input-Output Ports?

They are what connect input and output devices (Keyboard, Mouse,Printer, Scanner, Monitor etc.) to the computer.

Types of Input-Output (I/O) ports

Serial Port

PS/2

Parallel Printer Port

LAN Port

Audio Port

Universal serial Bus (USB)

Input Output Mapping

Input Output Mapping

Memory Mapped I/O

Isolated I/O

There are two types of Input Output Mapping

Memory & I/O Share the entire address range of processor.

Any machine instruction that can access memory can be used to

transfer data to or from an I/O device.

Memory control signals, used to control read & write I/O operations.

Memory Mapped I/O

Processor Provide separate Address Range for Memory & I/O.

Input Output control signals are used to control read and write

input output operations.

Isolated I/O

Memory Map Techniques

Memory Map Techniques

There are 3 types of Memory map Techniques

Direct Mapping

Fully Associative Mapping

Set –Associative Mapping

Simplest way of mapping.

Main memory is divided in blocks.

Maps each block of main memory into only one possible cache line.

Direct Mapping

Direct Mapping

Fully Associative Mapping

In associative cache mapping, the data from any location in

RAM can be stored in any location in cache.

When the processor wants an address, all tag fields in the

cache as checked to determine if the data is already in the

cache.

Each tag line requires circuitry to compare the desired

address with the tag field.

All fields are checked in parallel.

Fully Associative Mapping

Set associative mapping is a mixture of direct and associative mapping.

The cache lines are grouped into sets.

The number of lines in a set can vary from 2 to 16.

A portion of the address is used to specify which set will hold an

address.

The data can be stored in any of the lines in the set.

Set-Associative Mapping

Set Associative Mapping

V-Set Associative

Mapping

Set Associative Mapping

K-Set Associative

Mapping

Interrupt Driven I/O

What is Interrupt?

Event that disrupts the normal execution of a program and causes the

execution of special instructions.

Interrupt Driven I/O

In Interrupt Driven I/O approach, the processor issues an I/O command

to a module and then go on to do some other useful work.

The I/O module with then interrupt the processor to request service

when it is ready to exchange data with the processor. The processor

then executes resumes its former processing.

Simple Interrupt Processing

Advantages of Interrupt Driven I/O

I/O is important aspect for communicating.

Interrupt adapts to the processor speed and I/O device, automatically.

Drawbacks of Interrupt Driven I/O

The I/O transfer rate is limited by the speed with which the processor

can test and service a device.

Needs continues intervention of processor, so it consumes time.

DMA Based I/O

What is DMA?

DMA – Direct Memory Access

In this method the input and output devices read/write information from

the main memory without interference of the CPU through the system

bus.

Block Diagram of DMA

DMA Operation

The processor issues a command to DMA module

Read or write

I/O device address using data lines

Starting memory address using data lines – stored in address

register

Number of words to be transferred using data lines – stored in

data register

DMA Operation (Cont.)

The processor then continues with other work.

DMA module transfers the entire block of data – one word at a time –

directly to or from memory without going through the processor.

DMA module sends an interrupt to the processor when complete.

Configuration of DMA

Single-bus, Detached DMA

Single-bus, Integrated DMA

I/O Bus

Advantages of DMA

Fast transfer of data.

CPU and DMA run concurrently under cache mode.

DMA can trigger an interrupt, which frees the CPU so the speed

increases.

Input Output Channels and

Processors

Input Output Channels and Processors

I/O processor is an extension of the concept of DMA. The I/O

processor can execute specialized I/O program residing in the memory

without intervention of the CPU.

CPU only needs to specify a sequence of I/O activity to I/O processor

An advanced I/O processor can have its own memory, enabling a large

set of I/O devices to be controlled without much involvement from the

CPU.

Types of I/O channels

Controls multiple high-speed devices

Dedicated to the transfer of data with one of the devices

Each device handled by a controller or I/O module

I/O channel controls these I/O controllers

1.) Selector Channel

Types of I/O channels

2.) Multiplexor Channel

Can handle multiple devices at the same time

Byte multiplexor – used for low-speed devices

Block multiplexor – interleaves blocks of data from several devices.

Advantages I/O channels

Makes transfers less visible to CPU, spreads the complexity

Can Improve speed

Can improve device organization flexibility

Conclusion

Input output devices gets connected to computer through I/O Ports.

There are Direct mapping, Fully Associative and Set-Associative

method techniques for mapping the memory.

There are various method of transferring data from Input output

devices to the memory or memory to Input Output devices.

Like : Interrupt Driven I/O, DMA Based I/O, Input Output

Processors.

Book : Computer Organization and Architecture by William Stallings

Images : Google Images

Reference

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