The Pangea IC implements two independent USB controllers (root hubs), each with two ports, for a total of four ports. The internal modem and the external USB port nearest the mini-VGA connector are connected to one controller; the other two USB ports are connected to the other controller.
Each USB controller provides a 12 Mbps data transfer rate that is shared between the two devices connected to it. The two USB ports that are connected to separate controllers can support high data rate devices at the same time with no degradation of their performance. Thus, if a user connects a high-speed (12 Mbps) device to USB port 1 and another high-speed device to the port 2, both devices can operate at their full data rates.
All three external USB connectors support USB devices with data transfer rates of 1.5 Mbps or 12 Mbps. For more information about the connectors, see "USB Ports".
USB devices connected to the iMac are required to support USB-suspend mode as defined in the USB specification. Information about the operation of USB-suspend mode on Macintosh computers is included in the Mac OS USB DDK API Reference. To obtain that document, please see the references at "USB Interface".
The USB ports on the iMac comply with the Universal Serial Bus Specification 1.1 Final Draft Revision. The USB controllers comply with the Open Host Controller Interface (OHCI) specification.