Abstract: A data cache memory apparatus permits load and store instructions to be issued out-of-order. The apparatus includes a memory. An instruction issue apparatus issues an instruction stream containing store and load instructions. The store instructions are completed in two passes, namely a store allocate pass and a corresponding store commit pass. A cache control is connected to the instruction issue apparatus and the memory and issues store and load addresses to the memory in response to instructions from the instruction issue apparatus. A store history table is connected to the cache control and stores a record of the addresses of the memory where data are to be stored, and thus a record of the store allocate passes issued by the instruction issue apparatus for which no corresponding store commit pass has been completed. The cache control responds to the subsequent corresponding store commit pass to issue the store address to the memory and to clear the store instruction from the store history table.

Abstract: In a computer system that contains plural computer resource elements, such as multiple processor and memory units, with those elements communicating digital information over a common communications bus, high communications bus efficiency is achieved. An interface permits each of said processor and memory elements to individually and independently access either the data bus, without busying the address bus, or the address bus without busying the data bus, with bus access being limited to a fixed interval of time. Different ones of said processor and memory units may thus simultaneously transfer digital information over the respective address and data bus. The foregoing system includes a bus contention and priority protocol to eliminate the possibility of data collision and includes identification lines for identifying each processor element accessing the bus.