SCISM: A scalable compound instruction set machine

Abstract

In this paper we describe a machine organization suitable for RISC and CISC architectures. The proposed organization reduces hardware complexity in parallel instruction fetch and issue logic by minimizing possible increases in cycle time caused by parallel instruction issue decisions in the instruction buffer. Furthermore, it improves instruction-level parallelism by means of special features. The improvements are achieved by analyzing instruction sequences and deciding which instructions will issue and execute in parallel prior to actual instruction fetch and issue, by incorporating preprocessed information for parallel issue and execution of instructions in the cache, by categorizing instructions for parallel issue and execution on the basis of hardware utilization rather than opcode description, by attempting to avoid memory interlocks through the preprocessing mechanism, and by eliminating execution interlocks with specialized hardware.