Technical information

CHAPTER 3
Devices and Ports
32 USB Ports
Version 1.2 of the Macintosh USB system software provides functions that
support all four transfer types.
USB Compatibility Issues 3
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.
Serial Port Compatibility 3
The latest release of the Mac OS USB DDK includes a universal Serial/USB
shim that allows processes that use the Communications Toolbox CRM to find
and use a USB modem device. The shim is called SerialShimLib and is available
as part of the Mac OS 8.6 release. 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 does not currently provide a USB Communication Class driver, so
modem vendors still need to write their own vendor-specific USB class drivers.
Macintosh-To-Macintosh Connections 3
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.
USB Storage Devices 3
The Macintosh USB software does not support booting from an external USB
storage device.
USB Controller 3
The computer uses an Open Host Controller Interface (OHCI) controller for
USB communication. Some early USB devices (most notably keyboards) can’t