Apple Desktop Computer manual

 T echnical Publications © Apple Computer , Inc. 1998  De veloper Note Apple iMac Computer Developer Note[...]

 Apple Computer , Inc. © 1998 Apple Computer , Inc. All rights reserved. No part of this publication may be repr oduced, stored in a retrieval system, or transmitted, in any form or by any means, mechanical, electronic, photocopying, r ecording, or otherwise, without prior written permission of Apple Computer , Inc., except to make a backup cop[...]

3 Contents Figures and T ables 7 Pref ace About This Dev eloper Note 9 Contents of This Note 9 Supplemental Reference Documents 10 PowerPC G3 Micropr ocessor 10 Mac OS 10 A T A Devices 10 USB Devices 1 1 Open Firmware 1 1 Chapter 1 Introduction 13 Features 14 Case and External Features 15 Compatibility Issues 18 System Software 18 Main RAM Expansio[...]

4 Infrared Link Module 26 Chapter 3 De vices and P or ts 27 USB Ports 28 USB Connectors 28 T ransfer T ypes Supported 29 USB Compatibility Issues 30 ADB Compatibility 30 Serial Port Compatibility 31 Macintosh-T o-Macintosh Connections 31 USB Storage Devices 31 USB Controller 31 Keyboard 32 Keyboard Layout 32 Keyboard and USB 33 Mouse 33 Hard Disk D[...]

5 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 Configuratio[...]

6 Interrupt Handling 64 Outmoded Resources 65 RAM Footprint 65 R T AS 65 NV -RAM 65 NanoKernel 66 Startup Disk Control Panel 66 Open Firmware and the Device T ree 67 Interrupt Layout 67 Machine Identification 67 Appendix Abbre viations 69 Inde x 73[...]

7 Figur es and T ables Chapter 1 Introduction 13 Figure 1-1 F ront vie w 16 Figure 1-2 Side view sho wing I/O ba y 17 Chapter 2 Architecture 21 Figure 2-1 Block diag ram 22 Chapter 3 De vices and P orts 27 Figure 3-1 USB T ype A por t and connector 29 Figure 3-2 ANSI ke yboard la yout 32 Table 3-1 Pin assignments on the USB por t 29 Table 3-2 Displ[...]

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9 PREF ACE About This Developer Note This developer note is a concise description of the iMac ™ computer , with the emphasis on the features that ar e new or differ ent from those of other Macintosh desktop computers. This developer note is intended to help hardwar e and software developers design products that ar e compatible with the products d[...]

10 PREF ACE Supplemental Refer ence Documents 0 For more information about the technologies mentioned in this developer note, you may wish to consult some of the following refer ences. P owerPC G3 Microprocessor 0 For more information about the PowerPC 750™ micr oprocessor used in the iMac computer , developers may wish to refer to the standar d [...]

11 PREF ACE USB De vices 0 For more information about USB on the Macintosh computer , developers should refer to Apple Computer ’s Mac OS USB DDK A TI Refer ence . Information is also available on the W orld W ide W eb, at: http://developer .apple.com/dev/usb/ For full specifications of the Universal Serial Bus, developers should refer to the US[...]

12 PREF ACE IEEE Std 1275-1994 Standard for Boot (Initialization, Configuration) Firmware (V ersion 1.7) Open Firmware Recommended Practice: Device Support Extensions (V ersion 1.0) Open Firmware Recommended Practice: Interrupt Mapping (V ersion 0.9)[...]

13 CHAPTER 1 Intr oduction 1 Figure 1-0 Listing 1-0 T able 1-0[...]

CHAPTER 1 Introduction 14 F eatures 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 . Featur es 1 Here is a list of the featur es of the iMac computer . Each feature is described in more detail in a later chapter . ■ Proce[...]

CHAPTER 1 Introduction Case and External Features 15 ■ Modem: The computer has a built-in modem with 56 Kbps data rate. For more information, see “Internal Modem” (page 39). ■ 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” (p[...]

CHAPTER 1 Introduction 16 Case and External Features Figure 1-1 F ront vie w The front of the case is dominated by the 15-inch display . The fr ont also includes, below the display , the following features: ■ CD-ROM drive opening, in the center , with a drawer eject button ■ Stereo speakers, one on either side ■ Infrared window , next to the [...]

CHAPTER 1 Introduction Case and External Features 17 Figure 1-2 Side view sho wing I/O ba y Sound input port Sound output port Universal Serial Bus (USB) ports (2) Ethernet port Hole for reset button Hole for programmer's button (NMI) Internal modem port[...]

CHAPTER 1 Introduction 18 Compatibility Issues The back of the case contains the receptacle for the power cor d 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 fr ont, contains the I/O bay behind a hinged cover . Figure 1-2 is a side view showing the I/O bay w[...]

CHAPTER 1 Introduction Compatibility Issues 19 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). IMPORT ANT The main RAM DIMMs in the iM[...]

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21 CHAPTER 2 Ar chitectur e 2 Figure 2-0 Listing 2-0 T able 2-0[...]

CHAPTER 2 Architecture 22 The components at the heart of the iMac computer reside on two printed-cir cuit boards: the main logic boar d and the processor module. The Figur e 2-1 is a block diagram showing the major components on those boards. The components shown are described in the sections that follow . Figure 2-1 Block diag ram Power switch and[...]

CHAPTER 2 Architecture Processor module 23 Pr ocessor module 2 The processor module contains the high-speed components: ■ G3 micropr ocessor ■ 512 KB backside cache memory ■ main memory (minimum of 32 MB) ■ system ROM (1 MB) ■ memory controller and the PCI bus bridge IC The devices on the processor module communicate with the main logic b[...]

CHAPTER 2 Architecture 24 Main Logic Board processor ’s clock speed, rather than at the clock speed of the main system bus. In the iMac, the clock speed of the backside cache is half that of the micropr ocessor . The data storage for the backside L2 cache consists of 512 KB of fast static RAM on the processor module. Memor y Controller and PCI Br[...]

CHAPTER 2 Architecture Main Logic Board 25 ■ the built-in modem ■ the infrared link ■ the Ethernet port ■ the sound ASIC ■ the internal IDE hard drive ■ the internal CD-ROM drive ■ the power manager IC The Paddington IC is similar to the Heathrow IC used in the Power Macintosh G3 computers and Macintosh PowerBook G3 computers. The mai[...]

CHAPTER 2 Architecture 26 Main Logic Board Infrared Link Module 2 The infrared link module is a separate printed cir cuit board that is connected to SCC port B of the Paddington IC. The maximum IrDA data transfer rate is 4 Mbit/sec.[...]

27 CHAPTER 3 Devices and Ports 3 Figure 3-0 Listing 3-0 T able 3-0[...]

CHAPTER 3 De vices and P orts 28 USB P orts This chapter describes both the built-in I/O devices and the ports for connecting external I/O devices. Each of the following sections describes an I/O port or device: ■ “USB Ports” ■ “Keyboard” ■ “Mouse” ■ “Hard Disk Drive” ■ “V ideo Display” ■ “Infrared Communication Li[...]

CHAPTER 3 De vices and P orts USB P orts 29 Figure 3-1 USB T ype A por t and connector The iMac computer provides 5-volt power at 500 mA for each of the two ports. The USB ports support both low-speed and high-speed data transfers, at up to 1.5 Mbits per second and 12 Mbits per second, respectively . High-speed operations requir es the use of shiel[...]

CHAPTER 3 De vices and P orts 30 USB P orts ■ Interrupt transfers, used for human interface device (HID) class devices such as keyboards and mice, as well as devices that r eport status changes, such as serial or parallel adaptors and modems. ■ Isochronous transfers, used for on-time delivery of data. Isochr onous data transactions are best sui[...]

CHAPTER 3 De vices and P orts USB P orts 31 Serial P or t Compatibility 3 The first release of the MacOS USB DDK does not include a universal Serial/ USB shim that would allow processes that use the Communications T oolbox CRM to use a USB serial device. At the introduction of the iMac computer , any USB Serial Class Driver will need to implement [...]

CHAPTER 3 De vices and P orts 32 K eyboard Keyboar d 3 The Apple USB keyboard has a total of 82 keys, including 12 function keys, a numeric keypad and a set of 4 cursor-contr ol keys. The cursor-contr ol keys are in the inverted-T arrangement. K e yboard La y out 3 There ar e versions of the Apple USB keyboard with dif fer ent key layouts for three[...]

CHAPTER 3 De vices and P orts Mouse 33 K e yboard and USB 3 The Apple USB keyboard is designed to work with the iMac computer by way of the USB ports. The keyboard has a captive cable with a USB T ype A connector . The keyboard is a bus-power ed USB hub with two USB T ype A ports. ▲ W A RNING A bus-power ed hub as defined in the USB specificati[...]

CHAPTER 3 De vices and P orts 34 Hard Disk Drive The mechanism inside the Apple USB mouse is similar to that in the Apple Desktop Bus Mouse II. The mouse ball is removeable for cleaning; the ring that allows access to the ball can be locked by inserting an unfolded paper clip into a small hole and turning the ring clockwise. Har d Disk Drive 3 The [...]

CHAPTER 3 De vices and P orts Infrared Communication Link 35 Infrar ed Communication Link 3 The iMac computer has a direct infrar ed (IR) communication link connected internally to serial port B. When the computer is placed within range of another device with an IR interface, it can send and receive serial data using the IrDA protocol. The other de[...]

CHAPTER 3 De vices and P orts 36 Sound System Sound Inputs 3 The sound system accepts inputs from thr ee possible sources: ■ built-in microphone ■ external stereo sound input jack ■ sound from internal CD player Built-in Microphone 3 The sound signal from the built-in micr ophone goes through a dedicated preamplifier that raises its signal l[...]

CHAPTER 3 De vices and P orts Sound System 37 ■ during power cycling Exter nal Sound Output 3 The external sound output jack is a 3.5-mm mini phone jack located in the I/O bay on the right side of the computer . It accepts a stereo miniplug-to-RCA cable adapter for connecting stereo equipment to the computer . The sound output jack has the follow[...]

CHAPTER 3 De vices and P orts 38 Sound System T otal harmonic distortion plus noise (THD+N) as a percentage of full scale for various outputs are shown in T able 3-3. The signal-to-noise ratios (SNR) for various inputs and outputs are shown in T able 3-4. The values shown are unweighted; values with A weighting would be about 8 dB higher . Table 3-[...]

CHAPTER 3 De vices and P orts Ethernet Port 39 Ethernet Port 3 The iMac computer has a built-in 10/100 Mbps Ethernet port. The user can connect it to either a 10Base-T or a 100Base-TX hub; the port will automatically sense which type of hub is connected. The connector for the Ethernet port is a an RJ-45 connector in the I/O bay on the right side of[...]

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41 CHAPTER 4 RAM Expansion 4 Figure 4-0 Listing 4-0 T able 4-0[...]

CHAPTER 4 RAM Expansion 42 The Expansion Slots This chapter tells how to gain access to the expansion slots in the iMac computer and describes the two types of RAM expansion: main RAM expansion and video RAM expansion. The Expansion Slots 4 T o get access to the expansion slots, the user must open up the bottom of the computer and remove the main l[...]

CHAPTER 4 RAM Expansion The Expansion Slots 43 Figure 4-1 Bottom view sho wing bottom cov er handle Removing the bottom co v er 4 The bottom cover is held in place by a retaining scr ew located on the bottom cover and accessible through the opening in the handle. After r emoving the screw , the user can remove the cover by pulling up and out on the[...]

CHAPTER 4 RAM Expansion 44 The Expansion Slots Figure 4-2 Cables connected to the logic board assemb ly[...]

CHAPTER 4 RAM Expansion The Expansion Slots 45 Removing the Retaining Scre ws 4 A slot-shaped handle is located at the back end of the logic boar d assembly . The retaining scr ews are located inside the slot in the handle, as shown in Figure 4-3. Figure 4-3 Logic board assembly handle and retaining scre ws Handle Retaining screws[...]

CHAPTER 4 RAM Expansion 46 The Expansion Slots Removing the Logic Board Assemb ly 4 W ith the r etaining screws r emoved and the cables positioned to the sides, the user can remove the logic boar d assembly by pulling upward on the handle, as shown in Figure 4-4. Figure 4-4 Removing the logic board assemb ly IMPORT ANT While removing and r einstall[...]

CHAPTER 4 RAM Expansion The Expansion Slots 47 Figure 4-5 EMI shield Locations of the Expansion Slots 4 Figure 4-6 shows the location of the two main RAM expansion slots and the video RAM expansion slot. One of the main RAM expansion slots is on the bottom of the processor module and is normally occupied by the factory-installed SO-DIMM. The other [...]

CHAPTER 4 RAM Expansion 48 Main RAM Expansion Figure 4-6 Locations of the RAM e xpansion slots Main RAM Expansion 4 The iMac computer has two RAM expansion slots that accommodate standard SO (small outline) DIMMs using SDRAM devices. IMPORT ANT RAM expansion SO-DIMMs for the iMac must use SDRAM devices. If the user installs an SO-DIMM that uses EDO[...]

CHAPTER 4 RAM Expansion Main RAM Expansion 49 T otal RAM capacity using devices currently available is 128 MB and is limited by the space available for the SO-DIMMs. The bottom slot can accommodate a 1.5-inch SO-DIMM. The top slot can accommodate a 2.0-inch SO-DIMM. Note Future devices with higher density may allow expansion beyond the current 128-[...]

CHAPTER 4 RAM Expansion 50 Main RAM Expansion The JEDEC specification for the SO-DIMM defines a Serial Presence Detect (SPD) feature that contains the attributes of the module. SO-DIMMs for use in the iMac are r equired to have the SPD featur e. Information about the requir ed values to be stored in the pr esence detect EEPROM is in section 4.1.2[...]

CHAPTER 4 RAM Expansion Main RAM Expansion 51 Configuration of RAM SO-DIMMs 4 T able 4-1 shows the sizes of the RAM expansion modules that can be used in the iMac computer and the differ ent sizes of SDRAM devices that make up those modules. The iMac accepts either one or two SO-DIMMs. Any of the supported SO-DIMM sizes can be installed in either [...]

CHAPTER 4 RAM Expansion 52 Main RAM Expansion Address Multiple xing 4 Signals A[0] – A[13] on each RAM SO-DIMM make up a 14-bit multiplexed address bus that can support several dif ferent types of SDRAM devices. T able 4-2 lists the types of devices that can be used in the iMac computer by size, configuration, and sizes of row and column addr es[...]

CHAPTER 4 RAM Expansion Video RAM Expansion 53 Active 1.2 A (8 devices at 150 mA each) Sleep 6 mA per bank The maximum current specified for active operation generally r ules out the use of 4-bit-wide SDRAM devices in a RAM expansion card. Such a car d would have 16 such devices, and the 1.2 A maximum current would allow only about 75 mA per devic[...]

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55 CHAPTER 5 Softwar e 5 Figure 5-0 Listing 5-0 T able 5-0[...]

CHAPTER 5 Software 56 Wh y Make This Change? The Apple iMac computer is differ ent from pr evious Macintosh computers in that it has no single, large ROM that contains the toolbox softwar e, the 68K emulator , hardwar e initialization, and the nanokernel. A small ROM pr ovides hardwar e initialization functions and pr ovides a mechanism to load the[...]

CHAPTER 5 Software Wh y Make This Change? 57 • Not changing the higher level software as often simplifies things for many groups inside Apple, including testing, system softwar e, software configuration management, developer support, and publications. Third-party developers can also benefit from this. What Has Changed 5 Hardwar e-specific cod[...]

CHAPTER 5 Software 58 Wh y Make This Change? F eatures of the Ne w Approach 5 Because the iMac has new hardwar e features that ar e differ ent fr om other Macintosh computers, new software featur es are needed in addition to the NewW orld requirements for other Macintosh computers. This list includes features that implement the NewW orld approach a[...]

CHAPTER 5 Software Wh y Make This Change? 59 P erf ormance 5 Performance of an iMac computer using ROM in RAM should exceed performance measurements for other Macintosh computers with comparable CPUs and speeds due to improved interr upt handling with the New W orld approach. In addition, performance is impr oved due to executing code that normally[...]

CHAPTER 5 Software 60 Boot ROM Contents in RAM appears to be a ROM, the ROM-in-RAM approach is completely compatible with all application and system software. The Mac OS T oolBox image is kept in a file in the System Folder on the specified boot device. In order to avoid pr oblems with internationalizing the name, the file is located by file ty[...]

CHAPTER 5 Software Boot ROM Contents 61 Failure to boot in POST causes the err or beep, optionally entering the Mini-Nub. Open Fir mware 5 The Open Firmware component of NewW orld is based on the CHRP version of Open Firmware, also known as Open Firmwar e 3.0. This is the most robust and full-featured Open Firmwar e used by Apple to date. This vers[...]

CHAPTER 5 Software 62 T oolbo x Image File Contents R T AS is relocateable code; its location in RAM is determined by the OS, and it remains functional after the OS boots. Note R T AS is part of the system software. It is not needed by applications, which use operating system APIs. ◆ T oolbox Image File Contents 5 The T oolbox image file (also ca[...]

CHAPTER 5 Software NewW orld Boot Process 63 T rampoline Code 5 The T rampoline code is the component of the NewW orld architectur e that handles the transition between Open Firmware and the T oolBox ROM Image. It retrieves all necessary information about the system fr om Open Firmware, instantiates R T AS, decompresses the T oolBox ROM Image, loca[...]

CHAPTER 5 Software 64 What Is Diff erent 5. The Forth script transfers control to the T rampoline code, which functions as the transition between Open Firmware and the beginning of the Mac OS execution; 6. The T rampoline code decompresses the T oolBox ROM Image, gathers information about the system from Open Firmwar e, creates data str uctures bas[...]

CHAPTER 5 Software What Is Diff erent 65 that interrupt latency has been r educed to such an extent as to make it negligible. The other is that the interrupt handling code no longer r equires changes to support a new machine, unless it has new interrupt contr oller hardwar e. The description of the interrupt layout is now part of an Open Firmware i[...]

CHAPTER 5 Software 66 What Is Diff erent variable-sized partitions that are used by Mac OS, Open Firmwar e, and any other client. PRAM resides in the Mac OS partition. The partitioning scheme is part of the CHRP specification. NanoK ernel 5 The previous version of the NanoKernel has code that is pr ocessor-specific to create data str uctures. Und[...]

CHAPTER 5 Software What Is Diff erent 67 Once Open Firmware locates a startup device and successfully loads a Mac OS ROM, image it passes information about the chosen device in the bootpath variable. This information, rather than that previously set in PRAM, is subsequently used by the Mac OS ROM to locate the device containing the startup System F[...]

CHAPTER 5 Software 68 What Is Diff erent T oolBox ROM Image, so sharing the same Box Flag is not an issue for those areas. IMPORT ANT Programs such as contr ol panels and installers that use Box Flag to verify that this is a valid CPU on which to execute need to be changed to verify the existence of the hardwar e they requir e. Developers should lo[...]

69 APPENDIX Abbr eviations A Standard units of measur e used in this note include: Other abbreviations used in this note include: A amperes MB megabytes dB decibels Mbps megabits per second GB gigabytes Mbit megabits Hz hertz MHz megahertz KB kilobytes mm millimeters kg kilograms ns nanoseconds kHz kilohertz V volts mA milliamperes VDC volts direct[...]

APPENDIX A Abbre viations 70 CHRP Common Hardwar e Reference Platform CPU central pr ocessing unit CRM Communications Resource Manager CR T cathode ray tube, a video display device DAA data access adapter (a telephone line interface) DAC digital-to-analog converter DIMM Dual Inline Memory Module DMA direct memory access EDO extended data out EEPROM[...]

APPENDIX A Abbre viations 71 NMI nonmaskable interrupt NV -RAM nonvolatile random-access memory OHCI Open Host Controller Interface OS operating system PCI Peripheral Component Interconnect, an industry-standard expansion bus PLL phase-locked loop POST power-on self test RAM random-access memory RAID random array of inexpensive disks RCA Radio Corp[...]

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73 Index A A T A Device Software Guide 10, 34 A T A disk interface 34 A T A hard disk 34 A TI Rage IC 25 B backside cache 23 Boot ROM 57 contents 60–62 Box Flag 68 C cache, See backside cache case 15 compatibility 18–19 custom ICs Paddington 24 D device tree 67 E ethernet port 39 external features 15 F features list 14 G G3 micropr ocessor 23 g[...]

INDEX 74 K keyboard 32–33 L L2 cache 23 M machine ID 67 Macintosh ROM, why it’s changing 56–60 Mac OS 8.1 10 Mac OS ROM file 59 Mac OS ROM image 58 Mac OS T oolBox ROM 57 main logic board 24–26 memory controller IC 24 memory interleaving not supported 51 micropr ocessor 23 modem 25, 39 mouse 33–34 MPC106 IC 24 N NanoKernel 66 'ndrv&[...]

INDEX 75 Run-T ime Abstraction Services. See RT AS S SDRAM device specifications 50 serial presence detect, on SO-DIMM 50 SGRAM 53 SO-DIMMs, for RAM expansion 48 address multiplexing on 52 configurations 51 electrical design of 49 electrical limits for 52 JEDEC specifications 49 mechanical design of 49 SDRAM device specifications 50 sound input[...]

THE APPLE PUBLISHING SYSTEM This Apple manual was written, edited, and composed on a desktop publishing system using Apple Macintosh computers and FrameMaker software. Line art was created using Adobe ™ Illustrator and Adobe Photoshop. T ext type is Palatino ® and display type is Helvetica ® . Bullets are ITC Zapf Dingbats ® . Some elements, s[...]