The Power Mac G4 computer does not include certain I/O features found on some older Macintosh computers.
The Power Mac G4 computer does not include built-in internal or external SCSI device connectors. Adding an internal or external SCSI device requires the use of a SCSI PCI card. Ultra2 SCSI (LVD) drives and PCI controller cards are available as options at the time of purchase.
The Power Mac G4 computer does not include RS-422 LocalTalk serial ports found on older Macintosh models. Serial I/O for external USB devices is provided by two USB ports. USB adapters are available from third parties to support Macintosh-compatible legacy serial devices.
The USB ports take the place of the ADB and serial I/O ports found on older Macintosh computers. Software shims have been implemented in the system software to allow existing applications that use ADB devices to work with USB devices.
The Power Mac G4 computer uses a USB keyboard and mouse similar to the USB keyboard and mouse introduced with the iMac computer.
USB game controllers are supported by the InputSprocket component of the Apple Games Sprockets software architecture. InputSprocket software and information about the InputSprocket APIs can be found at