Abstract: An instruction pipeline in a microprocessor is provided. The instruction pipeline includes a plurality of pipeline units, each of the plurality of pipeline units processing a plurality of instructions. At least two of the plurality of pipeline units are a source of at least some of the instructions for the pipeline. The pipeline further includes at least two speculative return address stacks, each of the speculative return address stacks coupled is coupled to at least one of the instruction source units. Each of the speculative return return address stacks are capable of storing at least two speculative return addresses.

Abstract: An instruction pipeline in a microprocessor is provided. The instruction pipeline includes a plurality of pipeline units, each of the plurality of pipeline units processing a plurality of instructions. At least two of the plurality of pipeline units are a source of at least some of the instructions for the pipeline. The pipeline further includes at least two speculative return address stacks, each of the speculative return address stacks coupled is coupled to at least one of the instruction source units. Each of the speculative return return address stacks are capable of storing at least two speculative return addresses.

Abstract: A method and apparatus for providing a non-blocking cache that uses substantially less die area than a prior art non-blocking cache. In the present invention, pending count and ignore fill fields are added to each line of the cache. These fields are used in conjunction with a valid field (that indicates whether or not the line contains valid data) to keep track of the status of pending load operations that have resulted in cache misses. The pending field keeps a count of the number of outstanding load misses for the line. If a store occurs for an address of a line, the ignore fill field is set to indicate that any fills that are pending for the line are to be ignored because the pending fills will be supplying stale data to the line.