The specification of an embedded system at system level together with co-joint hardware/software synthesis is a goal of many rapid prototyping projects. SDL has been proposed as a formal and abstract specification language well suite d for this purpose. The implementation of SDL's asynchronous communication model in application specific hardware, however, is un-proportionally expensive in terms of area and response time. This paper discusses the efficiency of the server model - the implementation model used in all known codesign approaches based on SDL - and compares it with an alternative implementation model for SDL known from software, the activity thread model. In a combination of both implementation strategies, the communication and synchronization overhead for each application can be minimized, and an efficient implementation on distributed architectures realized. The integration in an existing rapid prototyping design process is presented as well as results gained from application examples.