1. An apparatus comprising: a speculative store buffer memory; and a speculative store buffer controller configured to receive store instructions, wherein the speculative store buffer controller comprises: a store address comparator configured to compare an address of one of the received store instructions with addresses of store instructions allocated in the speculative store buffer memory; and a store age comparator configured to compare an age of the one of the received store instructions with an age of one of the store instructions allocated in the speculative store buffer memory responsive to the store address comparator finding a match between the address of the one of the received store instructions and the address of the one of the store instructions, wherein the speculative store buffer controller is configured to replace the one of the store instructions allocated in the speculative store buffer memory with the one of the received store instructions responsive to the one of the store instructions allocated in the speculative store buffer memory being younger than the one of the received store instructions.