Open source RISC processor for system on a chip applications

This paper presents a simple RISC processor that allows the user to add customized instructions to accelerate key algorithms. The new instructions are added by modifying the HDL description of the processor. The processor can be programmed and the added instructions can be accessed through a high level language. The use of such features is demonstrated through examples of Reed Solomon decoding and the Log-MAP algorithm used in decoding Turbo codes. The examples show that considerable improvements in performance can be achieved by adding specific specialized instructions. Such features should be of use in future system on a chip applications that will require such algorithms to be implemented efficiently.