The other method, strangely named statistical multiplexing, allows the devices to be identified whenever a command for them arrives from the OS, and likewise when they sent data to the OS. An id number is appended to every command from the OS and every response from the device has an id number attached to it. This method makes more sense than round robin if not all the devices are equally active or if the attached devices are a little faster than they could be in round robin. An especially active peripheral might send a lot of data to the CPU while the others are inactive, and in statistical multiplexing it wouldn't have to wait until its next time slot rolled around.