STRUCTURE AND METHOD FOR ACHIEVING VERY LARGE LOOKAHEAD INSTRUCTION WINDOW VIA NON-SEQUENTIAL INSTRUCTION FETCH AND ISSUE

A multithreading processor achieves a very large lookahead instruction window by allowing non-sequential fetch and processing of the dynamic instruction stream. A speculative thread is spawned at a specified point in the dynamic instruction stream and the instructions subsequent to the specified point are speculatively executed so that these instructions are fetched and issued out of sequential order. Very minimal modifications to existing processor design of a multithreading processor are required to achieve the very large lookahead instruction window. The modifications include changes to the control logic of the issue unit, only three additional bits in the register scoreboard.