The Universal Serial Bus or USB has become a very popular choice for connecting external devices to a PC, laptop, handheld or embedded device. Although found everywhere, not so many people fully understand USB. The new USB stack which I’ve designed for FreeBSD-8 and FreeBSD-9 is not like any other USB stack. In addition to being an USB stack it is also a multiprocessor safe USB stack. In my talk about USB I will try to explain some details about USB itself, the FreeBSD-8/9 USB API’s and general concepts I’ve built around with regard to achieving multiprocessor operation.