PATHDocumentation > Hardware > Power Mac G4 Developer Note


FireWire Controller

The PCI bus supports an IEEE 1394a FireWire controller with a maximum data rate of 400 Mbits (50 MBytes) per second. The controller implements the FireWire link layer. A physical layer IC, called a PHY, implements the electrical signaling protocol of the FireWire interface. The PHY supports three FireWire ports. Two of the ports go to external connectors on the rear panel of the base unit. The third port is available for devices inside the case.

The computer is capable of accepting external power through the FireWire connector to operate the PHY when the computer is turned off. While the PHY is operating, it acts as a repeater from one port to another so that the FireWire bus remains connected. For more information, see FireWire Ports.


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