International Business Machines Corporation
Method to determine the oldest instruction in an instruction queue of a processor with multiple instruction threads

Abstract:

A method to determine an oldest instruction in an instruction queue of a processor with multiple instruction threads, wherein each of the multiple instruction threads have a unique thread identifier. The method includes tagging each instruction thread, of the multiple instruction threads, in the instruction queue with a unique tag number according to a round-robin scheme, wherein the unique tag number includes the unique thread identifier for each instruction thread and a round number in the round-robin scheme. The method further includes selecting, for each instruction thread, of the multiple instruction threads, the instruction thread with a lowest tag number from the multiple instruction threads in the instruction queue that are tagged with an oldest round number from the round-robin scheme.