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Developer Note
Apple iMac Computer
Developer Note
Technical Publications
© Apple Computer, Inc. 1998
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Apple Computer, Inc. may be registered in certain jurisdictions. © 1998 Apple Computer, Inc. All rights reserved. Helvetica and Palatino are registered trademarks of Linotype-Hell AG No part of this publication may be and/or its subsidiaries. reproduced, stored in a retrieval system, or transmitted, in any form ITC Zapf Dingbats is a registered or by any means, mechanical, trademark of International Typeface electronic, photocopying, recording, Corporation. or otherwise, without pri
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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 Ca
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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
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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? 5
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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
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Figures and Tables Chapter 1 Introduction 13 Figure 1-1 Front view 16 Figure 1-2 Side view showing I/O bay 17 Chapter 2 Architecture 21 Figure 2-1 Block diagram 22 Chapter 3 Devices and Ports 27 Figure 3-1 USB Type A port and connector 29 Figure 3-2 ANSI keyboard layout 32 Table 3-1 Pin assignments on the USB port 29 Table 3-2 Display resolutions and pixel depths 35 Table 3-3 Distortion specifications 38 Table 3-4 Noise specifications 38 Chapter 4 R
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PREF ACE About This Developer Note ™ This developer note is a concise description of the iMac computer, with the emphasis on the features that are new or different from those of other Macintosh desktop computers. This developer note is intended to help hardware and software developers design products that are compatible with the products described here. If you are not already familiar with Macintosh computers or if you would simply like additional technical information, y
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PREF ACE Supplemental Reference Documents 0 For more information about the technologies mentioned in this developer note, you may wish to consult some of the following references. PowerPC G3 Microprocessor 0 For more information about the PowerPC 750™ microprocessor used in the iMac computer, developers may wish to refer to the standard reference, PowerPC 740/750 Microprocessor Implementation Definition Book IV. Information about the PowerPC 750 and other G3 microprocessor
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PREF ACE USB Devices 0 For more information about USB on the Macintosh computer, developers should refer to Apple Computer’s Mac OS USB DDK ATI Reference. Information is also available on the World Wide Web, at: http://developer.apple.com/dev/usb/ For full specifications of the Universal Serial Bus, developers should refer to the USB Implementation Forum on the World Wide Web, at: http://www.usb.org/developers/index.html Open Firmware 0 Three Technotes provide an introduc
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PREF ACE IEEE Std 1275-1994 Standard for Boot (Initialization, Configuration) Firmware (Version 1.7) Open Firmware Recommended Practice: Device Support Extensions (Version 1.0) Open Firmware Recommended Practice: Interrupt Mapping (Version 0.9) 12
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CHAPTER 1 Figure 1-0 Introduction 1 Listing 1-0 Table 1-0 13
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CHAPTER 1 Introduction The Apple iMac computer is a new consumer-oriented desktop computer. This chapter summarizes the features of this new computer and points out issues affecting compatibility. Features 1 Here is a list of the features of the iMac computer. Each feature is described in more detail in a later chapter. n Processor: The iMac has a PowerPC G3 microprocessor running at a clock speed of 233 MHz. For more information, see “G3 Microprocessor”
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CHAPTER 1 Introduction n Modem: The computer has a built-in modem with 56 Kbps data rate. For more information, see “Internal Modem” (page 39). n Ethernet: The computer has a built in Ethernet port for a 10Base-T and 100Base-TX operation with an RJ-45 connector. For more information, see “Ethernet Port” (page 39). n Infrared link: The computer has an IrDA infrared link capable of transferring data at up to 4 Mbits per second. For more information, see “Infrared
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CHAPTER 1 Introduction Figure 1-1 Front view Microphone CD-ROM drive Infrared window Power button on computer Stereo speaker Headphone jacks (2) Stereo speaker Apple USB keyboard Open button on CD-Rom drive Power button on keyboard Apple USB mouse The front of the case is dominated by the 15-inch display. The front also includes, below the display, the following features: n CD-ROM drive opening, in the center, with a drawer eject button n Stereo speakers, one on either side
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CHAPTER 1 Introduction Figure 1-2 Side view showing I/O bay Ethernet port Universal Serial Bus (USB) ports (2) Hole for reset button Sound output port Hole for programmer's Sound input port button (NMI) Internal modem port Case and External Features 17
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CHAPTER 1 Introduction The back of the case contains the receptacle for the power cord and a small folding handle for use in removing the access cover on the bottom of the case. The right side of the case, as viewed from the front, contains the I/O bay behind a hinged cover. Figure 1-2 is a side view showing the I/O bay with its cover open. The I/O bay contains the following features: n Sound input and output jacks n Two USB ports n Ethernet port n Modem connector n Ac
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CHAPTER 1 Introduction Main RAM Expansion Modules 1 For expansion of main RAM, the iMac computer uses standard SO-DIMMs that contain SDRAM devices. These are similar to the SO-DIMMs used in the Macintosh G3 PowerBook Series. For more information, see “Main RAM Expansion” (page 48). IMPORTANT The main RAM DIMMs in the iMac must be SO-DIMMs that use SDRAM devices. SO-DIMMs that use EDO or SGRAM devices will not work. s Video RAM Expansion Modules 1 For expansion of video RAM
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