Parallel data processing in a single processor

A system allows parallel data processing within a single processor. In order to allow for parallel processing of data, an arithmetic logic unit (26) or other operation executing entity within the processing system such as a shifter (29) is partitioned. Within each partition (41,51), operations are performed on a portion of one or more operands. When the operation is to be performed on full word length operands, there is no parallel processing. Thus data is allowed to freely propagate across boundaries between the partitions (41,51). When performing the operation in parallel using a plurality of operands of less than one full word in length, data is prevented from being propagated across at least one boundary between the partitions (41,51). The principles of the present invention may also be utilized to implement a multiplier (301-316,320) which performs parallel multiplication of partial word multiplicands.