The present invention sets forth a method and system for communicating with an external device through a processing unit in a graphics system of a computing device. In one embodiment, the method comprises allocating a first set of memory buffers having a first memory buffer and a second memory buffer in the graphics system based on an identification information of the external device, and invoking a first thread processor of the processing unit of the graphics system to perform services associated with a physical layer according to the identification information of the external device by storing a first data stream received from the external device through an I/O interface of the processing unit of the graphics system in the first memory buffer and retrieving a second data stream from the second memory buffer for transmission to the external device through the I/O interface.