All USB drivers are integrated in the code, and that one isn't there, and can't be added. Realtek don't use accelerated i/o devices. All the interfaces are simple, and the throughput is limited by the power of the CPU to copy data to and from buffers. The cost of the CPU is kept low by limiting it's throughput ability to that needed to stream off a BD player. All these chips are BD player chips. ARM based players are using off the shelf chip designs never intended for BD players, and hence with much higher performance.
