Instruction Fetch Policies for SMT Processors Based on EPIC

Explicitly parallel instruction computing(EPIC) can decrease the complexity of hardware,and simultaneous multithread(SMT) has the unique ability to exploit TLP(Thread Level Parallelism),so great benefit can be obtained by combining these two techniques.Fetch policies are of great importance to the overall performance of SMT processors.This paper describes several prevailing fetch policies used in superscalar SMT processors,analyses their applicability for EPIC SMT processors,and proposes a novel fetch policy called SICOUNT(Stop ICOUNT) suitable for EPIC SMT.Detailed analysis indicates that SICOUNT strategy can take full advantage of the HW/SW Co-design characteristic of EPIC.It achieves this by taking into account the stop hints generated by EPIC compiler.This makes it easier for SICOUNT to evaluate the flowing speed of each thread more precisely,and to fetch instructions with better quality.