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TitleDevice Management
LanguageEnglish
File Size1.6 MB
Total Pages52
Table of Contents
                            Device types
DASD
Components of IO subsystem
Communication
	Polling & Interrupts
	DMA
	Buffers
Management of IO requests
Device Handling Algorithms
	FCFS
	SSTF
	SCAN
RAID
summary
                        
Document Text Contents
Page 1

Operating Systems
Lecture #4: IO Management

Written by David Goodwin
based on the lecture series of Dr. Dayou Li

and the book Understanding Operating Systems 4
th

ed.
by I.M.Flynn and A.McIver McHoes (2006)

Department of Computer Science and Technology,
University of Bedfordshire.

Operating Systems, 2013

18th February 2013

Page 2

52

Lecture #4 IO
Management

David Goodwin
University of
Bedfordshire

Device types

DASD

Components of IO
subsystem

Communication

Polling & Interrupts

DMA

Buffers

Management of IO
requests

Device Handling
Algorithms

FCFS

SSTF

SCAN

RAID

summary

Operating Systems

Outline

1 Device types

2 DASD

3 Components of IO subsystem

4 Communication
Polling & Interrupts
DMA
Buffers

5 Management of IO requests

6 Device Handling Algorithms
FCFS
SSTF
SCAN

7 RAID

8 summary

Page 26

52

Lecture #4 IO
Management

David Goodwin
University of
Bedfordshire

Device types

DASD

Components of IO
subsystem

Communication

26Polling & Interrupts

DMA

Buffers

Management of IO
requests

Device Handling
Algorithms

FCFS

SSTF

SCAN

RAID

summary

Operating Systems

INTERRUPTS

� CPU Interrupt-request line triggered by I/O device

� Interrupt handler receives interrupts

� Maskable to ignore or delay some interrupts

� Interrupt vector to dispatch interrupt to correct handler
� Based on priority
� Some unmaskable

� Interrupt mechanism also used for exceptions

Page 27

cycle.eps


52

Lecture #4 IO
Management

David Goodwin
University of
Bedfordshire

Device types

DASD

Components of IO
subsystem

Communication

27Polling & Interrupts

DMA

Buffers

Management of IO
requests

Device Handling
Algorithms

FCFS

SSTF

SCAN

RAID

summary

Operating Systems

INTERRUPT-DRIVEN I/O CYCLE

Page 51

52

Lecture #4 IO
Management

David Goodwin
University of
Bedfordshire

Device types

DASD

Components of IO
subsystem

Communication

Polling & Interrupts

DMA

Buffers

Management of IO
requests

Device Handling
Algorithms

FCFS

SSTF

SCAN

RAID

51summary

Operating Systems

Key Terms

access time

blocking

buffers

channel status word (CSW)

C-LOOK

C-SCAN

direct access storage Device (DASD)

direct memory access (DMA)

first-come, first-served (FCFS)

IO channel

IO channel program

IO contol unit

IO device handler

IO scheduler

Page 52

52

Lecture #4 IO
Management

David Goodwin
University of
Bedfordshire

Device types

DASD

Components of IO
subsystem

Communication

Polling & Interrupts

DMA

Buffers

Management of IO
requests

Device Handling
Algorithms

FCFS

SSTF

SCAN

RAID

52summary

Operating Systems

Key Terms

IO subsystem

IO traffic controller

interrupt

LOOK

N-step SCAN

parity bit

RAID

SCAN

search

search time

seek strategy

seek time

shortest seek time first (SSTF)

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