Apple Desktop Computer manual Compatibility Issues, System Software

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C H A P T E R 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:

■Sound input and output jacks

■Two USB ports

■Ethernet port

■Modem connector

■Access to programmer’s buttons through two small openings (upper one for reset, lower one for NMI)

The bottom of the case has a hinged support that can be used to tilt the front of the computer upward by about 17 degrees.

The back portion of the bottom of the case is a removable plastic cover, retained by a screw, that can be removed to allow access to the main logic board and drive assembly. That entire assembly can be removed for installation of expansion RAM.

Compatibility Issues

While the iMac computer has many new features, there should be no compatibility problems with applications that operate correctly with earlier Macintosh models. Compatibility issues for expansion and peripheral devices are listed here.

System Software

The iMac computer has newly designed system software that provides Open Firmware booting and Mac OS ROM in RAM. The system software is described in Chapter 5. For software compatibility information, see “Compatibility” (page 59).

18Compatibility Issues

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Contents Apple iMac Computer Page Contents Devices and Ports RAM ExpansionSoftware RtasAppendix Abbreviations Index Rtas NV-RAMFigures and Tables Page Contents of This Note About This Developer NoteMac OS PowerPC G3 MicroprocessorSupplemental Reference Documents ATA DevicesUSB Devices Open FirmwareE F a C E Introduction Features Case and External Features Shows a front view of the computerFront view 2Side view showing I/O bay Compatibility Issues System SoftwareMain 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 Connectors USB PortsTransfer Types Supported GNDUSB Compatibility Issues ADB CompatibilityUSB Storage Devices Serial Port CompatibilityMacintosh-To-Macintosh Connections USB ControllerKeyboard Keyboard LayoutMouse Keyboard and USBHard Disk Drive Video DisplayInfrared Communication Link Sound SystemBuilt-in Microphone Sound InputsSound Outputs External Sound InputSound Speciﬁcations External Sound OutputHeadphone Jacks Total harmonic distortion Ethernet Port Internal ModemPage RAM Expansion Removing the Logic Board Assembly Expansion SlotsPlacing the Computer Face Down Removing the bottom cover Unfastening the CablesRAM Expansion 3Logic board assembly handle and retaining screws Removing the Retaining ScrewsRemoving the Logic Board Assembly Removing the EMI ShieldLocations of the Expansion Slots Main RAM Expansion 6Locations of the RAM expansion slotsMechanical Design of RAM SO-DIMMs Electrical Design of RAM SO-DIMMsSdram Devices Conﬁguration of RAM SO-DIMMs RAM SO-DIMM Electrical Limits Address MultiplexingVideo RAM Expansion Page Software Why Make This Change? What Has Changed Features of the New Approach User Experience PerformanceRAM Footprint Data Structures and FilesBoot ROM Contents Mac OS ndrv Drivers RtasToolbox Image File Contents NewWorld Boot Process Trampoline CodeToolBox ROM Image What Is Different Interrupt HandlingOutmoded Resources RAM FootprintNanoKernel Startup Disk Control PanelOpen Firmware and the Device Tree Interrupt LayoutMachine Identiﬁcation Software Abbreviations Chrp NMI Page Index Nvram X, Y, Z Allen Watson