What are the benefits of dual-channel USB? Is there anything else new with regards to USB?

The Power Mac G4 (AGP Graphics) and iMac (Slot-Loading) incorporate a separate 12-Mbps USB controller for each USB port. Now there is the potential to connect up to 127 devices to each port, as opposed to earlier USB-enabled Macintosh computers that support up to 127 devices connected to both USB ports.

What's New to USB?

Beginning with the Power Mac G4 (AGP Graphics) and the iMac (Slot-Loading), two new features to USB are most apparent: support for USB audio devices and booting from USB drives.

USB Audio Devices: This includes any device also that supports the Isochronous USB protocol (which are mostly Audio in nature). This includes USB speakers, microphones, and other recording/playback devices.

Bootable USB drives: A storage device such as a SuperDisk, Zip disk, or other USB storage drive can be used to hold a valid system folder and used at startup.

USB Specifications

• two Universal Serial Bus (USB) Type A ports
• a maximum of 500 Milliamps (mA) at 5 volts (V) is available per port, for a total of 1 ampere.
• data transfer rates:
  • low-speed: 1.5 megabits per second (Mbps) maximum
  • high-speed: 12 Mbps maximum