A technique for operating a processor includes storing a first result to a writeback buffer, in response to a first execution unit of the processor attempting to write the first result of a first completed instruction to a register file of the processor at a same processor time as a second execution unit of the processor is attempting to write a second result of a second completed instruction to the register file. The writeback buffer is positioned in a dataflow between the first execution unit and the register file. A buffer full indicator logic is used to detect that the writeback buffer is unavailable. A buffer unavailable signal is transmitted, from the buffer full indicator logic, in response to detecting the writeback buffer is unavailable. In response to receiving the buffer unavailable signal, a buffer retrieving logic writes the first result from the writeback buffer to the register file.