This paper describes the current implementation and experimental results of a hardware/software codesign system for ASIP (Application Specific Integrated Processor) development： the PEAS-I System. The PEAS-I system accepts a set of application programs written in C language, associated data set, module database, and design constraints such as chip area and power consumption. The system then generates an optimized CPU core design in the form of an HDL as well as a set of application program development tools such as a C compiler, an assembler and a simulator. Another important feature of the PEAS-I system is that the system is able to give accurate estimations of chip area and performance before the detailed design of the ASIP is completed. According to the experimental results, the PEAS-I system has been found to be highly effective and efficient for ASIP development.