Warning A bus-powered hub as defined in the USB specification does not provide enough power to support a second bus-powered hub. A second bus-powered hub must be connected to the second USB port on the computer, not to a port on the Apple USB keyboard.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 on the front of the computer. 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).