Overlapped macro instruction control system

Abstract

A system for overlapping macro instruction execution is described for use in a data processing system. A pair of control storage devices each store the micro instruction sets required to execute all macro instructions in the repertoire and are used for alternate macro instructions. Each of the controlled storage devices is addressable to entry addresses by the macro instructions. After entry, addressing is by the contents of the micro instructions with provision made for conditional branching. An overlap count storage device is provided for storing overlap counts for all possible sequences of macro instructions. These overlap counts define the number of micro instructions of the current macro instruction that must be executed before the next macro instruction can proceed. Micro instruction execution is by clock cycle and are counted as they are executed. The count is compared to the stored overlap count for the current sequence of macro instructions and overlap execution is enabled when comparison is found. Overlap of macro instruction execution is allowed to occur when the current remaining micro instructions for the current macro instruction define functions that are mutually exclusive with the functions controlled by the next macro instruction. During overlap, micro instructions are loaded in an execution register from both control storage devices. Overlapping instructions that have variable execution sequences is controlled by halting the count of micro instruction executions until the variable sequence has been completed.