Apple Desktop Computer manual About This Developer Note, Contents of This Note

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P R E F A C E

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, you may wish to read the section “Supplemental Reference Documents”.

Contents of This Note

The information in this note is arranged in ﬁve chapters.

■Chapter 1, “Introduction,” introduces the iMac computer and describes its features.

■Chapter 2, “Architecture,” describes the internal logic of the computer, including the main ICs.

■Chapter 3, “Devices and Ports,” describes the I/O ports and the built-in I/O devices.

■Chapter 4, “RAM Expansion,” describes the expansion features of interest to developers. It includes development guides for the RAM expansion modules.

■Chapter 5, “Software,” describes the system software that comes with the computer, with emphasis on the new Open Firmware features.

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Contents Apple iMac Computer Page Contents RAM Expansion Devices and PortsRtas SoftwareRtas NV-RAM Appendix Abbreviations IndexFigures and Tables Page About This Developer Note Contents of This NoteSupplemental Reference Documents PowerPC G3 MicroprocessorMac OS ATA DevicesOpen Firmware USB DevicesE F a C E Introduction Features Shows a front view of the computer Case and External FeaturesFront view 2Side view showing I/O bay System Software Compatibility IssuesMain RAM Expansion Modules Video RAM Expansion ModulesUSB Ports and Devices Page Architecture Architecture Processor module G3 MicroprocessorBackside Cache Main Logic Board Memory Controller and PCI BridgeController IC USB Controller Video Display SubsystemBuilt-in Modem Infrared Link Module Devices and Ports USB Ports USB ConnectorsGND Transfer Types SupportedADB Compatibility USB Compatibility IssuesMacintosh-To-Macintosh Connections Serial Port CompatibilityUSB Storage Devices USB ControllerKeyboard Layout KeyboardKeyboard and USB MouseVideo Display Hard Disk DriveSound System Infrared Communication LinkSound Outputs Sound InputsBuilt-in Microphone External Sound InputSound Speciﬁcations External Sound OutputHeadphone Jacks Total harmonic distortion Internal Modem Ethernet PortPage RAM Expansion Removing the Logic Board Assembly Expansion SlotsPlacing the Computer Face Down Unfastening the Cables Removing the bottom coverRAM Expansion Removing the Retaining Screws 3Logic board assembly handle and retaining screwsRemoving the EMI Shield Removing the Logic Board AssemblyLocations of the Expansion Slots 6Locations of the RAM expansion slots Main RAM ExpansionElectrical Design of RAM SO-DIMMs Mechanical Design of RAM SO-DIMMsSdram Devices Conﬁguration of RAM SO-DIMMs Address Multiplexing RAM SO-DIMM Electrical LimitsVideo RAM Expansion Page Software Why Make This Change? What Has Changed Features of the New Approach RAM Footprint PerformanceUser Experience Data Structures and FilesBoot ROM Contents Rtas Mac OS ndrv DriversToolbox Image File Contents NewWorld Boot Process Trampoline CodeToolBox ROM Image Interrupt Handling What Is DifferentRAM Footprint Outmoded ResourcesStartup Disk Control Panel NanoKernelOpen Firmware and the Device Tree Interrupt LayoutMachine Identiﬁcation Software Abbreviations Chrp NMI Page Index Nvram X, Y, Z Allen Watson