Micro-threading: a new approach to future RISC

Abstract

This paper briefly reviews the current research into RISC microprocessor architecture, which now seems to be so complex as to make the acronym somewhat of an oxymoron. In response to this development we present a new approach to RISC micro-architecture named micro-threading. Micro-threading exploits instruction-level parallelism by multi-threading but where the threads are all assumed to be drawn from the same context and are thus represented by just a program counter. This approach attempts to overcomes the limit of RISC instruction control (branch, loop, etc.) and data control (data miss, etc.) by providing such a low context switch time that it can be used not only to tolerate high latency memory but also avoid speculation in instruction execution. It is therefore able to provide a more efficient approach to instruction pipelining. In order to demonstrate this approach we compile simple examples to illustrate the concept of micro-threading within the same context. Then one possible architecture of a micro-threaded pipeline is presented in detail. At last, we give some comparisons and a conclusion.