Abstract: With the rising of the open instruction set RISC-V, a number of open source and commercial soft cores have emerged, which are used in different fields such as IoT hardware, embedded systems, artificial intelligence chips, security devices, and high-performance computers. How to better balance between performance, power consumption, and chip area requires that the instruction set can be easily tailored, extended, and supported by the software development environment. To this end, this paper proposes a quick customization method for RISC-V processor, through adding custom instructions, extending ALU functional units, connecting control signals and data paths, FPGA prototype verification, customizing the cross compiler and application testing. Taking the matrix calculation acceleration as an example, a customized instruction for the vector inner production is designed on the open source IP Hummingbird E203, finishes the prototype verification on FPGA. The matrix calculation benchmark shows that the performance of the customized RISC-V processor has been significantly improved. For matrix multiplication, the performance speedup reaches 5.3~7.6.

Key words: RISC-V, instruction set, customization, processor, FPGA