A computer system consists of hardware, system programs, and application programs figs 5

MULTIPROCESSORS 8.2 MULTICOMPUTERS 8.3 DISTRIBUTED SYSTEMS 8.4 RESEARCH ON MULTIPLE PROCESSOR SYSTEMS 8.5 SUMMARY

5 INPUT/OUTPUT

5.1 PRINCIPLES OF I/O HARDWARE

5.2 PRINCIPLES OF I/O SOFTWARE

5.3 I/O SOFTWARE LAYERS

5.4 DISKS

5.5 CLOCKS

5.6 CHARACTER-ORIENTED TERMINALS 5.7 GRAPHICAL USER INTERFACES

5.8 NETWORK TERMINALS

5.9 POWER MANAGEMENT

5.10 RESEARCH ON INPUT/OUTPUT

5.11 SUMMARY

Two address One address space Two address spaces

Memory

I/O ports 0xFFFF…

0

Fig 5-2 (a) Separate I/O and memory space (b) Memory-mapped I/O (c) Hybrid.

CPU Memory I/O

Bus All addresses (memory

and I/O) go here

CPU reads and writes of memory

go over this high-bandwidth bus

This memory port is

to allow I/O devices access to memory

Fig 5-3 (a) A single-bus architecture (b) A dual-bus memory architecture.

DMA controller

Disk controller

Main memory Buffer

1 CPU programs the DMA controller

Interrupt when done

2 DMA requests transfer to memory 3 Data transferred

Bus

4 Ack

Address Count Control

Drive

Fig 5-4 Operation of a DMA transfer.

Interruptcontroller

3 CPU acks interrupt

2 Controller issues interrupt

1 Device is finished

Disk

Keyboard

PrinterClock

Bus

12 6

9 3 8 5 7

1 11 2 10

Fig 5-5 How an interrupt happens The connections between the devices and the interrupt controller actually use interrupt lines on the bus rather than dedicated wires.

Printed page

(a)

ABCD EFGH

ABCD EFGH

Printed page

(b)

A Next

(c)

AB Next

Fig 5-6 Steps in printing a string.

copy3from3user(buffer, p, count); /*p is the kernel bufer*/

for (i = 0; i < count; i++) { /*loop on every character*/

while (*printer3status3reg != READY) ;/*loop until ready*/

*printer3data3register = p[i]; /*output one character*/

}

return3to3user( );

Fig 5-7 Writing a string to the printer using programmed I/O.

copy3from3user(buffer, p, count); if (count == 0) {

enable3interrupts( ); unblock3user( );

while (*printer3status3reg != READY) ; } else {

*printer3data3register = p[0]; *printer3data3register = p[i];

i = i + 1;

}acknowledge3interrupt( );

return3from3interrupt( );

Fig 5-8 Writing a string to the printer using interrupt-driven I/O (a) Code executed when the print system call is made (b) Inter- rupt service procedure.

copy3from3user(buffer, p, count); acknowledge3interrupt( );

set3up3DMA3controller( ); unblock3user( );

scheduler( ); return3from3interrupt( );

Fig 5-9 Printing a string using DMA (a) Code executed when the print system call is made (b) Interrupt service procedure.

User-level I/O software Device-independent operating system software

Device drivers Interrupt handlers Hardware

Fig 5-10 Layers of the I/O software system.

Rest of the operating system

Printerdriver

Camcorderdriver

CD-ROMdriver

Printer controllerHardware

Devices

Camcorder controller CD-ROM controller

Fig 5-11 Logical positioning of device drivers In reality all communication between drivers and device controllers goes over the bus.

Operating system Operating system

Disk driver Printer driver Keyboard driver Disk driver Printer driver Keyboard driver

Fig 5-13 (a) Without a standard driver interface (b) With a dard driver interface.

Fig 5-14 (a) Unbuffered input (b) Buffering in user space.

(c) Buffering in the kernel followed by copying to user space (d) Double buffering in the kernel.

4

3User process

Network

Networkcontroller

request

Layer

I/Oreply I/O functionsMake I/O call; format I/O; spooling

Naming, protection, blocking, buffering, allocation

Set up device registers; check status

Wake up driver when I/O completed

Perform I/O operation

User processes

Device-independentsoftwareDevice drivers

Interrupt handlers

Hardware

Fig 5-16 Layers of the I/O system and the main functions of each layer.

Fig 5-17 Disk parameters for the original IBM PC 360-KB

floppy disk and a Western Digital WD 18300 hard disk.

0 1 2

3

5 6

1415

2 3 4 5 6 7

9 1 11 12 13 14 15 16 17 18

5

7

89 10 11

12 13 14 15 16

1 7

1 2 21 22

Fig 5-18 (a) Physical geometry of a disk with two zones.

(b) A possible virtual geometry for this disk.

P16-19 Strip 16 Strip 17 Strip 18

Strip 4

Strip 0

Strip 9 Strip 5 Strip 1

Strip 10 Strip 6 Strip 2

RAID level 2

Strip 11 Strip 7 Strip 3

Strip 8

Strip 4

Strip 0

Strip 9 Strip 5 Strip 1

Strip 10 Strip 6 Strip 2

Strip 11 Strip 7 Strip 3

Strip 8 Strip 4 Strip 0

Strip 9 Strip 5 Strip 1

Strip 10 Strip 6 Strip 2

Strip 11 Strip 7 Strip 3

RAID level 1

Strip 10 Strip 6 Strip 2

Strip 11 Strip 7 Strip 3

Strip 8

Strip 4

Strip 0

Strip 9 Strip 5 Strip 1

P8-11 Strip 6 Strip 2

Strip 10 P4-7 Strip 3

Strip 19 Strip 15

Strip 11 Strip 7 P0-3

Fig 5-19 RAID levels 0 through 5 Backup and parity drives are shown shaded.

Spiral groove

PitLand

2K block ofuser data

Fig 5-20 Recording structure of a compact disc or CD-ROM.

Frames of 588 bits,each containing

24 data bytes

Symbols of

14 bits each

42 Symbols make 1 frame

98 Frames make 1 sector

…

…

Fig 5-21 Logical data layout on a CD-ROM.

Printed label

Protective lacquerReflective gold layer

layer

SubstrateDirection

Infraredlaserdiode

Dark spot in thedye layer burned

by laser whenwriting1.2 mm

Dye

Polycarbonate

Fig 5-22 Cross section of a CD-R disk and laser (not to scale).

A silver CD-ROM has a similar structure, except without the dye layer and with a pitted aluminum layer instead of a gold layer.

Polycarbonate substrate 1

Polycarbonate substrate 2

Semireflective layer

Semireflective layer

Aluminum reflector

Aluminum reflector

Preamble Data ECC

Fig 5-24 A disk sector.

0 1 2 3 4 5 6 7

9 10

11

12 13

1 41 51 61 71 81 92 0 21 22

24 25 26

2930 31

0 1 2 3 4

6 7 8 9 10 11 12 13 14

15 16

17

1 8 1

345678911 121314116

181 2

2122

23 24 2

5

23 24

252627229 3

01234567 8910

11

1

1 3

1

11819

22

222324226 2

293310123456 7

89

10

111151617

19 20 21 2 232

262 282930 31 0 123456 7

9

1

11213

14

rotation

Fig 5-25 An illustration of cylinder skew.

5

(b)

07

52

41

36

(c)

05

14

36

27

Fig 5-26 (a) No interleaving (b) Single interleaving (c) Double interleaving.

Initial position

Pending requests

Initial position

3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

1

Old

2 Disk

ECC error

Fig 5-30 Analysis of the influence of crashes on stable writes.

Crystal oscillator

Counter is decremented at each pulse

Holding register is used to load the counter

Fig 5-31 A programmable clock.

Fig 5-32 Three ways to maintain the time of day.

Current time Next signal Clock

CPU Memory

RS-232interface

(a) (b)

Terminal

data structure

Terminal data structure

Terminal Terminal

Central buffer pool

area for terminal 0

area for terminal 1

CPU Memory

Graphics

controller Video

RAM

Analog video signal Parallel port

Bus

Fig 5-38 With memory-mapped displays, the driver writes directly into the display’s video RAM.

80 characters (a)

Fig 5-39 (a) A video RAM image for a simple monochrome

display in character mode (b) The corresponding screen The × s are attribute bytes.

Fig 5-40 A sample window located at (200, 100) on an XGA display.

#include <windows.h>

int WINAPI WinMain(HINSTANCE h, HINSTANCE, hprev, char*szCmd, int iCmdShow){

WNDCLASS wndclass; /*class object for this window*/

MSG msg; /*incoming messages are stored here*/

HWND hwnd; /*handle (pointer) to the window object*/

/*Initialize wndclass*/

wndclass.lpfnWndProc = WndProc; /*tells which procedure to call*/

wndclass.lpszClassName = "Program name"; /*Text for title bar*/

wndclass.hIcon = LoadIcon(NULL, IDI3APPLICATION);/*load program icon*/wndclass.hCursor = LoadCursor(NULL, IDC3ARROW); /*load mouse cursor*/RegisterClass(&wndclass); /*tell Windows about wndclass*/

hwnd = CreateWindow ( ) /*allocate storage for the window*/

ShowWindow(hwnd, iCmdShow); /*display the window on the screen*/UpdateWindow(hwnd); /*tell the window to paint itself*/

while (GetMessage(&msg, NULL, 0, 0)) { /*get message from queue*/

TranslateMessage(&msg); /*translate the message*/

DispatchMessage(&msg); /*send msg to the appropriate procedure*/

case WM3CREATE: ; return ; /*create window*/

case WM3PAINT: ; return ; /*repaint contents of window*/case WM3DESTROY: ; return ; /*destroy window*/

0 0

Fig 5-42 An example rectangle drawn using Rectangle Each box

represents one pixel.

2 4 6 8

Window 1

Window 2

0 2 4 6 8

0 2 4 6 8 0

2 4 6 8

Remote host Window

manager

Application program Motif

Intrinsics Xlib

X client UNIX Hardware

X server UNIX Hardware

X terminal

Window User

#include <X11/Xlib.h>

#include <X11/Xutil.h>

main(int argc, char*argv[])

{

int running = 1;

disp = XOpenDisplay("display3name"); /*connect to the X server*/

win = XCreateSimpleWindow(disp, ); /*allocate memory for new window*/XSetStandardProperties(disp, ); /*announces window to window mgr*/

gc = XCreateGC(disp, win, 0, 0); /*create graphic context*/

XSelectInput(disp, win, ButtonPressMask | KeyPressMask | ExposureMask);XMapRaised(disp, win); /*display window; send Expose event*/

while (running) {

XNextEvent(disp, &event); /*get next event*/

switch (event.type) {

case Expose: ; break; /*repaint window*/

case ButtonPress: ; break; /*process mouse click*/

case Keypress: ; break; /*process keyboard input*/

}

}

XFreeGC(disp, gc); /*release graphic context*/

XDestroyWindow(disp, win); /*deallocate window’s memory space*/

XCloseDisplay(disp); /*tear down network connection*/

}

Fig 5-46 A skeleton of an X Window application program.

Computer center

Dedicatednetworkconnection

Switch

Disks

Thin clientServer(s)

Fig 5-47 The architecture of the SLIM terminal system.