Apple Desktop Computer manual USB Compatibility Issues, ADB Compatibility

Page 30

C H A P T E R 3

Devices and Ports

■Interrupt transfers, used for human interface device (HID) class devices such as keyboards and mice, as well as devices that report status changes, such as serial or parallel adaptors and modems.

■Isochronous transfers, used for on-time delivery of data. Isochronous data transactions are best suited for audio or video data streams.

Version 1.0 of the Macintosh USB system software provides functions that support only control, bulk, and interrupt transfer types.

USB Compatibility Issues

The USB ports take the place of the ADB and serial I/O ports found on earlier Macintosh computers, but they do not function the same way. The following sections describe the differences.

ADB Compatibility

Apple is providing an ADB/USB shim to support processes that control ADB devices by making calls to the ADB Manager and the Cursor Device Manager. The ADB/USB shim makes it possible for processes that support an ADB keyboard to work with the USB keyboard equivalent.

For example, the ADB/USB shim allows applications to set the caps lock and num lock LEDs on the Apple USB keyboard. The ADB/USB shim also allows the Cursor Device Manager to support a USB mouse.

Keyboards other than the Apple USB keyboard can be used with the iMac computer, but they will be treated as having an ADB device ID of 2.

IMPORTANT

The ADB/USB shim does not support other types of ADB devices. ▲

Note

The ADB/USB shim is built into the Mac OS ROM image on the iMac computer and will be included in the Mac OS ROM image on future Power Macintosh systems that have USB ports. For more information about the Mac OS ROM image, refer to Chapter 5, “Software.” ◆

30USB Ports

Image 30

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