Keyboard and USB

The Apple USB keyboard is designed to work with the iMac family of computers by way of the USB ports. The keyboard has a captive cable with a USB Type A connector. The keyboard is a bus-powered USB hub with two USB Type A ports.

WARNING

A bus-powered hub does not provide enough power to support a second bus-powered hub. To use a second bus-powered hub with an iMac computer, connect it to the second USB port on the computer, not to a port on the Apple USB keyboard.

Power to the computer can be turned on using the keyboard power button. A proprietary circuit allows the power control circuitry on the main logic board to detect a power-button press and turn on the power.

The standard NMI and reset key combinations are available, but the keys are decoded in software and may not be available under some crashed conditions. Therefore, NMI and reset switches are also available in the computer's I/O panel.

Apple provides a HID class driver for the Apple USB keyboard, which supports the USB boot protocol. Other keyboards intended for use on the Macintosh platform must support the HID boot protocol, as defined in the USB Device Class Definition for Human Interface Devices (HIDs).