Specifications

USB Connectors

The USB ports use USB Type A connectors, which have four pins each. Two of the pins are used for power and

two for data. Figure 3-1 (page 31) shows the connector and Table 3-1 (page 31) shows the signals and pin

assignments.

Figure 3-1 USB connector

Table 3-1 Signals on the USB connector

DescriptionSignal namePin

+5 VDCVCC1

Data –D–2

Data +D+3

GroundGND4

The Power Mac G5 computer provides 5 V power for the USB ports and up to 500 mA on each port. The power

is provided in both run and sleep mode. The ports share the same power supply; a short circuit on one disables

all ports until the short has been removed.

The USB ports support all USB 2.0 speeds: high-speed (480 Mbps) and classic USB speeds of full-speed (12

Mbps) and low-speed (1.5 Mbps). High-speed operation requires the use of shielded cables.

The Macintosh system software supports all four data transfer types defined in the USB specification, as well

as split transactions for classic-speed devices attached to high-speed hubs.

Waking Up From Sleep

As defined in the USB-suspend mode of the USB specification, USB devices can provide a remote wakeup

function for the computer (resume signalling). The USB root hub in the computer is set to support remote

wakeup whenever a device is attached to the bus. The device wakes the computer by sending a RESUME event

to the USB root hub. The mouse and keyboard that come with the computer use this method to wake the

computer on a key press or mouse click.

Input and Output Devices

USB Ports