Apple Desktop Computer manual Architecture

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C H A P T E R 2

Architecture

The components at the heart of the iMac computer reside on two printed-circuit boards: the main logic board and the processor module. The Figure 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 diagram

Processor module

RAM

SO-DIMM

RAM

SO-DIMM

Modem module

Modem Datapump DAA controller

Telephone connector

512 KB

Backside

RAM

L2 cache

ROM

PowerPC

Data

Grackle

memory

G3

Address

controller

micro-

and PCI

processor

bus bridge

	Internal	Rage IIc
	video
		video
	monitor
		DAC

SGRAM

Main logic board

PCI bus	Paddington
PCI bus	I/O and
	I/O and
		disk
	controller

Burgundy sound I/O

Cuda

power

manager

IC

ST10040

Ethernet IC

Internal microphone

Sound in

Sound out

Speakers

Headphone jack board

Internal CD-ROM drive

Internal IDE disk drive

IrDA board

Power switch and LED

Ethernet connector

SGRAM SO-DIMM

USB IC

USB port 1

USB port 2

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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 SoftwareVideo RAM Expansion Modules Main RAM Expansion ModulesUSB Ports and Devices Page Architecture Architecture G3 Microprocessor Processor moduleBackside Cache Memory Controller and PCI Bridge Main Logic BoardController IC Video Display Subsystem USB ControllerBuilt-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 InputExternal Sound Output Sound SpeciﬁcationsHeadphone Jacks Total harmonic distortion Ethernet Port Internal ModemPage RAM Expansion Expansion Slots Removing the Logic Board AssemblyPlacing 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 Trampoline Code NewWorld Boot ProcessToolBox ROM Image What Is Different Interrupt HandlingOutmoded Resources RAM FootprintNanoKernel Startup Disk Control PanelInterrupt Layout Open Firmware and the Device TreeMachine Identiﬁcation Software Abbreviations Chrp NMI Page Index Nvram X, Y, Z Allen Watson