This paper presents the system synthesis techniques available in S 3 E 2 S, a CAD environment for the specification, simulation, and synthesis of embedded electronic systems that can be modeled as a combination of analog parts, digital hardware, and software. S 3 E 2 S is based on a distributed, object-oriented system model, where objects are initially modeled by their abstract behavior and may be later refined into digital or analog hardware and software. System synthesis is targeted to a multiprocessor platform. Each processor, either a custom-designed one or an off-the-shelf component, can have a specialized behavior, like signal processing or control processing. The environment selects processors that best match the desired application by analyzing and comparing processor and application characteristics. The paper illustrates the architecture selection process with concrete examples.