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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may be registered in certain jurisdictions.

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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

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