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 provides 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 PowerBook computer, but they will be treated as having an ADB device ID of 2.

IMPORTANT

The ADB/USB shim does not support USB devices other than the Apple USB keyboard and mouse.

Note
The ADB/USB shim is built into the Mac OS ROM image on the PowerBook computer, as it is on all Power Macintosh systems that have USB ports.

Serial Port Compatibility

The system software includes a serial shim, called SerialShimLib, that enables processes that use the Communications Toolbox CRM to find and use a USB modem device. For more information about the shim, and a sample modem driver that shows how to use it, please refer to the Mac OS USB DDK, available from the Apple Developer Development Kits page on the World Wide Web, at

http://developer.apple.com/sdk/

Apple also provides a USB Communication Class driver, so modem vendors whose devices comply with the USB Communication Class specification do not need to write their own vendor-specific USB class drivers. See USB Drivers.

Not for Networking

USB is a serial communications channel, but it does not replace LocalTalk functionality on Macintosh computers; you cannot connect two Macintosh computers together using the USB. The best method for networking PowerBook computers is through the built-in Ethernet port.