While research has shown that the agile chip design methodology is promising to sustain the scaling of computing performance in a more efficient way, it is still of limited usage in actual applications due to two major obstacles: 1) Lack of tool-chain and developing framework supporting agile chip design, especially for large-scale modern processors. 2) The conventional verification methods are less agile and become a major bottleneck of the entire process. To tackle both issues, we propose MINJIE, an open-source platform supporting agile processor development flow. MINJIE integrates a broad set of tools for logic design, functional verification, performance modelling, pre-silicon validation and debugging for better development efficiency of state-of-the-art processor designs. We demonstrate the usage and effectiveness of MINJIE by building two generations of an open-source superscalar out-of-order RISC-V processor code-named XIANGSHAN using agile methodologies. We quantify the performance of XIANGSHAN using SPEC CPU2006 benchmarks and demonstrate that XIANGSHAN achieves industry-competitive performance.

This paper introduces the microarchitecture and logical implementation of SMT (Simultaneous Multithreading) improvement of Godson-2 processor which is a 64-bit, four-issue, out-of-order execution high performance processor. The condition for implementing correct memory consistency model in Godson-2 SMT processor is studied and a new register-level sharing and synchronization scheme is proposed. Godson-2 SMT processor has been implemented at the RTL level and simulated with the VstationPro of Mentor Graphics. The Linux operating system is ported to run in Godson-2 SMT processor and application programs such as SPEC CPU2000 benchmark suite are used to evaluate performance. Experimental results indicate that the performance of Godson-2 SMT processor is improved significantly by fully exploiting thread-level parallelism and optimized utilization of functional units. The average speedup is 31.3% with 18.8% area overhead.