Course : AIT 204

Course Title : Computer Organization and Architecture (COA)

Course Credits : 3 + 0

Course Teacher : Dr. Y R Ghodasara & Prof. K.C. Kamani

College of Agricultural Information Technology

Anand Agricultural University

Anand

Unit IV

Intro to the I/O system

• I/O Devices are attached with the computer to communicate with the external world.

• Input devices are used to take input from the user.

• Output devices are used to display output to the user.

• Storage devices are used to store files.

• I/O Devices are connected with the south bridge of the mother board.

• Different I/O devices are using different I/O Bus for Connectivity.

• I/O bus is a standard mechanism to connect I/O device to transfer data.

• Separate Controllers are there to control I/O Bus.

Criteria North Bridge Bus South Bridge Bus

Devices CPU, RAM, AGP,

Ethernet

All other devices

Bus Options FSB

PCI Express

AGP

PCI

PCI Express

USB

ATA

SATA

SCSI

FireWire(WiFi)

Clock Speed 70-1000 MHz 10-40 MHz

Data Transfer Speed 3 GB/Second 20-500 MB/Second

Comparison of North Bridge and South Bridge Buses

Bus Type Devices

Serial, KBD, PS2 Keyboard, Mouse, Floppy

ROM,CMOS BIOS

ATA, SATA Hard disk, CD-ROM/RW, DVD

PCI/ PCI Express Network Card, Sound Card, Graphics and Video

Card and other Adapters

USB Mouse, Scanner, Printer, External Hard Disk,

Modam and many more

FireWire(Wi-Fi) Scanner, Camera, External Disk

SCSI Hard Disks, CD Drive, DVD Drive, Scanners

LPT, COM Keyboard, Mouse, Printers

Different Bus Interface to connect Devices

I/O devices Data Transfer Methods

Three methods are used to transfer data between memory and I/O devices.

• Programmed I/O transfer

• Interrupted I/O transfer

• DMA (Direct Memory Access ) transfer

Programmed I/O Transfer In the programmed I/O method, the I/O devices does not have direct access to memory.

A transfer from an I/O device to memory requires the execution of several instructions by the CPU.

CPU transfers data from I/O devices to its register and then write those data from register to

memory.

I/O

Controller

CPU RAM

Issue Read

Command to IO

Controller

Read Status of IO

Controller

status

Read Data from IO

Controller

Write Data to Memory

done

Not Ready

Ready

No

Yes

Execute Next Instruction

Check status

Disadvantages

• Continuous CPU Monitoring is required to check whether data is available from IO device or not.

This wastes lot of precious CPU cycles.

• Transfer from IO controller to CPU and CPU to Memory requires CPU execution time.

• Not suitable for large amount of data transfer.

Interrupted I/O Transfer In the interrupt I/O method, the I/O device controller will generate interrupt when device is ready to

transfer data. On receiving this interrupt, the CPU will execute IO routine stored in the memory to

transfer data and then resumes its former processing.

I/O

Controller

CPU RAM

Interrupt Received

Interrupt Raised

CPU doing something

else

IO Controller

Interrupt for

Data trasnfer

Interrupted

Read Data from IO

Controller

Write Data to Memory

done

No

Yes

Advantages

• Continuous CPU Monitoring is not required. IO controller request(interrupt) for CPU when ever

required. CPU can execute other programs in free time.

Disadvantages

• Transfer from IO controller to CPU and CPU to Memory requires CPU execution time.

• Not suitable for large amount of data transfer.

DMA (Direct Memory Access)Transfer In the DMA transfer, the I/O device is instructed by the CPU to transfer data.

CPU also provide location information and number of bytes to be transferred.

IO Controller will transfer data directly in the Memory using data bus.

CPU is free during this transfer and can do execution of other program.

IO Controller will inform CPU after transfer is complete.

I/O Controller

CPU RAM

Transfer Data From

location x1 ( 100

bytes ) to

x2(Memory) Transfer Complete

CPU Inform IO

Controller to transfer

data from x1(size) to

x2

CPU

Starts

other work

IO Controller Reads

Data

Write Data to Memory

doneNo

Yes

Inform CPU

that transfer

is over.

Advantages

• Continuous CPU Monitoring is not required. IO controller request(interrupt) for CPU when ever

required. CPU can execute other programs in free time.

• Transfer from IO controller to Memory does not require CPU execution time. CPU remains free.

• It is suitable for large amount of data transfer.

Multi Processor Architecture

Industry Demands More Processing Power For

• Drug Design

• To simulate engineering model

• To general complex graphics in computer application

• To process large amount of historical data and predict future trend

• To predict financial and economical trends

Limitations of Single Processor Machine

• Clock speed can not be increase further.

• In Digital circuit maximum signal speed is as much as light speed.

• More speed generate more heat.

• Dual Core Chip uses one die in a single package and a die contains two core

units on the processor.

• Dual core has 4MB of shared L2 cache on the processor.

• On Intel dual-core CPUs the Front Side Bus is used for accessing the RAM

memory.

Dual Core Processor

Dual Core Processor

• Quad Core Chip uses two dies in a single package and each die is a dual core

unit, for a total of four cores on the processor.

• Each core still has 4MB of shared L2 cache for a total of 8MB L2 on the

processor.

• On Intel quad-core CPUs the Front Side Bus is used for accessing the RAM

memory and for the communication between each pair of cores.

Quad Core Processor

Quad Core Processor

Multiprocessor in Multi computers

Multiprocessor systems can be build by connecting hundred of computers with single

processor.

Computers co ordinate by various programming language facility like message passing.

This is a low cost solution to achieve 100 CPUs speed using ordinary computers.

Examples

Cluster Computing

Grid Computing

Cloud Computing

CLUSTER COMPUTINGA computer cluster is a group of tightly coupled computers

that work together closely so that in many respects it can be

viewed as though it were a single computer.

Clusters are commonly connected through fast local area

networks.

Clusters are usually deployed to improve speed and/or

reliability over that provided by a single computer, while typically

being much more cost effective than single computer the of

comparable speed or reliability .

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Characteristics of Cluster computing

• Tightly coupled systems

• Single system image

• Centralized Job management & scheduling system

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What is a Grid?

• Many definitions exist in the literature

• Early defs: Foster and Kesselman, 1998

“A computational grid is a hardware and software infrastructure that provides dependable, consistent, pervasive, and inexpensive access to high-end computational facilities”

• Kleinrock 1969:

“We will probably see the spread of ‘computer utilities’, which, like present electric and telephone utilities, will service individual homes and offices across the country.”

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3-point checklist (Foster 2002)

1. Coordinates resources not subject to centralized control

2. Uses standard, open, general purpose protocols and interfaces

3. Deliver nontrivial qualities of service

• e.g., response time, throughput, availability, security

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Grid Architecture

Autonomous, globally distributed computers/clusters

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Why do we need Grids?

• Many large-scale problems cannot be solved by a single computer

• Globally distributed data and resources

• Roughly on a grid, a server log in to a bunch ofcomputers (the grid), send them data and aprogram to run, and runs the program onthose computers, which sends the data backto the server when its done.

Characteristics of Grid Computing

• Loosely coupled (Decentralization)

• Diversity and Dynamism

• Distributed Job Management & scheduling

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Comparison of Grid Computing vs. Cluster Computing

• Grid computing is focused on the ability to supportcomputation across administrative domains sets it apart fromtraditional computer clusters or traditional distributedcomputing.

• Grids offer a way of using the information technologyresources optimally inside an organization. In short, it involvesvirtualizing computing resources.

• Grid computing is often confused with cluster computing.Functionally, one can classify grids into several types:Computational Grids (including CPU scavenging grids), whichfocuses primarily on computationally-intensive operations,and Data grids, or the controlled sharing and management oflarge amounts of distributed data.

Cloud computing

• Cloud computing is the use of computingresources (hardware and software) that aredelivered as a service over a network (typicallythe Internet). The name comes from the useof a cloud-shaped symbol as an abstraction forthe complex infrastructure it contains insystem diagrams. Cloud computing entrustsremote services with a user's data, softwareand computation.

Use

•Helps to use applications without installations.

•Access the personal files at any computer withinternet access.

•This technology allows much more efficientcomputation by centralizing storage, memory,processing and band width.