USB Info and Benefits of Dual-Channel USB

What are the benefits of dual-channel USB? Is there anything else new with regards to USB?
This article has been archived and is no longer updated by Apple.
Universal Serial Bus (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
Published Date: Feb 20, 2012