Apple Desktop Computer User Manual
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Developer Note

Apple iMac Computer

Developer Note

Technical Publications

© Apple Computer, Inc. 1998

Apple Computer, Inc.

© 1998 Apple Computer, Inc. All rights reserved.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, mechanical, electronic, photocopying, recording, or otherwise, without prior written permission of Apple Computer, Inc., except to make a backup copy of any documentation provided on CD-ROM.

The Apple logo is a trademark of Apple Computer, Inc.

Use of the “keyboard” Apple logo (Option-Shift-K)for commercial purposes without the prior written consent of Apple may constitute trademark infringement and unfair competition in violation of federal and state laws.

No licenses, express or implied, are granted with respect to any of the technology described in this book. Apple retains all intellectual property rights associated with the technology described in this book. This book is intended to assist application developers to develop applications only for Apple-labeledorApple-licensedcomputers.

Every effort has been made to ensure that the information in this manual is accurate. Apple is not responsible for typographical errors.

Apple Computer, Inc. 1 Infinite Loop Cupertino, CA 95014 408-996-1010

Apple, the Apple logo, Macintosh and Power Macintosh are trademarks of Apple Computer, Inc., registered in the United States and other countries.

iMac is a trademark of Apple Computer, Inc.

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Simultaneously published in the United States and Canada.

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Contents

 

Figures and Tables

 

7

 

 

 

Preface

About This Developer Note

 

9

 

 

 

 

 

 

 

Contents of This Note

9

 

 

 

 

Supplemental Reference Documents

10

 

PowerPC G3 Microprocessor

10

 

 

Mac OS

10

 

 

 

 

 

 

ATA Devices

10

 

 

 

 

 

USB Devices

11

 

 

 

 

 

Open Firmware

 

11

 

 

 

Chapter 1

Introduction

13

 

 

 

 

 

 

 

 

 

 

 

 

Features

14

 

 

 

 

 

 

Case and External Features

15

 

 

 

Compatibility Issues

18

 

 

 

 

System Software

 

18

 

 

 

 

Main RAM Expansion Modules

 

19

 

Video RAM Expansion Modules

 

19

 

USB Ports and Devices

19

 

 

Chapter 2

Architecture

21

 

 

 

 

 

 

 

 

 

 

 

Processor module

 

23

 

 

 

 

G3 Microprocessor

23

 

 

 

 

Backside Cache

 

23

 

 

 

 

Memory Controller and PCI Bridge

24

 

Main Logic Board

 

24

 

 

 

 

I/O Controller IC

24

 

 

 

 

USB Controller

 

25

 

 

 

 

Video Display Subsystem

25

 

 

 

Built-in Modem

 

25

 

 

 

3

 

Infrared Link Module

26

 

 

Chapter 3

Devices and Ports

27

 

 

 

 

 

 

 

 

 

 

 

USB Ports

28

 

 

 

 

 

 

USB Connectors

28

 

 

 

 

Transfer Types Supported

 

29

 

 

USB Compatibility Issues

 

30

 

 

ADB Compatibility

30

 

 

 

Serial Port Compatibility

31

 

 

Macintosh-To-Macintosh Connections

31

 

USB Storage Devices

31

 

 

 

USB Controller

31

 

 

 

 

Keyboard

32

 

 

 

 

 

 

Keyboard Layout

32

 

 

 

 

Keyboard and USB

33

 

 

 

 

Mouse

33

 

 

 

 

 

 

Hard Disk Drive

34

 

 

 

 

Video Display

34

 

 

 

 

 

Infrared Communication Link

35

 

 

Sound System

35

 

 

 

 

 

Sound Inputs

36

 

 

 

 

 

Built-in Microphone

36

 

 

 

External Sound Input

36

 

 

Sound Outputs

36

 

 

 

 

Internal Speakers

36

 

 

 

External Sound Output

 

37

 

 

Headphone Jacks

37

 

 

 

Sound Specifications

37

 

 

 

Ethernet Port

39

 

 

 

 

 

Internal Modem

39

 

 

 

 

Chapter 4 RAM Expansion

41

The Expansion Slots

42

Removing the Logic Board Assembly

42

4

Placing the Computer Face Down

42

Removing the bottom cover

43

 

Unfastening the Cables

43

 

 

Removing the Retaining Screws

45

Removing the Logic Board Assembly

46

Removing the EMI Shield

46

 

 

Locations of the Expansion Slots

47

 

Main RAM Expansion

48

 

 

 

Mechanical Design of RAM SO-DIMMs

49

Electrical Design of RAM SO-DIMMs

49

SDRAM Devices

50

 

 

 

Configuration of RAM SO-DIMMs

51

Address Multiplexing

52

 

 

RAM SO-DIMM Electrical Limits

52

 

Video RAM Expansion

53

 

 

 

Chapter 5 Software

 

55

 

 

 

Why Make This Change?

56

 

What Has Changed

57

 

Features of the New Approach

58

Performance

59

 

 

RAM Footprint

59

 

User Experience

 

59

 

Data Structures and Files

59

Compatibility

59

 

Boot ROM Contents

 

60

 

POST Code

60

 

 

 

Open Firmware

61

 

 

Mac OS 'ndrv' Drivers

61

 

RTAS

61

 

 

 

 

Toolbox Image File Contents

62

Open Firmware Script

62

 

Trampoline Code

63

 

ToolBox ROM Image

63

 

NewWorld Boot Process

63

 

What Is Different

64

 

 

5

 

Interrupt Handling

 

64

 

 

 

Outmoded Resources

65

 

 

 

RAM Footprint

65

 

 

 

 

RTAS

65

 

 

 

 

 

 

NV-RAM

 

65

 

 

 

 

 

NanoKernel

66

 

 

 

 

 

Startup Disk Control Panel

66

 

 

Open Firmware and the Device Tree

67

 

Interrupt Layout

67

 

 

 

 

Machine Identification

67

 

 

Appendix

Abbreviations

69

 

 

 

 

 

 

 

 

 

 

 

Index 73

6