Specifications of the USB 2.0 ports included with some Macintosh computers.
USB ports on the computer
Certain Macintosh models have up to three built-in USB Type A ports that comply with USB 2.0 specifications. Each built-in USB port can provide a data transfer rate of 480 megabits per second (Mbit/s).
You can connect either USB 1.1 or USB 2.0-compliant devices to the computer's USB 2.0 ports.
As with USB 1.1, you can connect up to 127 devices on each USB controller. You can use Apple System Profiler to identify which devices share the same USB controller.
The data transfer rates each port uses depends on whether the communication occurs at low-speed, mid-speed or high-speed. These rates are:
USB ports on the keyboard and display
The USB ports on your Apple Pro Keyboard or Apple Pro Keyboard (2003) are USB 1.1 compliant ports, allowing a 1.5 Mbit/s or 12 Mbit/s data transfer rate. Apple displays that have USB hubs (any monitor that uses an ADC connector) are also USB 1.1 compliant.
A USB 2.0-compliant device connected to the ports on the keyboard or a display do not operate at high speed. The device may operate at full speed (12 Mbit/s) if it has that capability.