Abstract: A method and apparatus for looking up source matches in a central processing unit (CPU) is utilized to identify dependencies between instructions that have been renamed via buffer renaming techniques. In such instances, when a particular instruction's source is a previous instruction's destination, that match needs to be identified such that dependent relationships between instructions are maintained. The source lookup method and apparatus utilize an allocation pointer and deallocation pointer, which point to the rename buffer, to produce a comparison window. For a given source of a given instruction, the comparison window is used to compare whether the source in question has a match within the rename buffer. If only one match is found, that rename buffer location is flagged to indicate that this particular location has a dependent relationship with the current source in question. If more than one match has been identified, a selection is made to choose the buffer location closest to the allocation pointer.