1. A method of operating a processor, comprising: in response to a first execution unit of the processor attempting to write a 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, storing the first result to a writeback buffer of the processor, wherein the writeback buffer is positioned in a dataflow between the first execution unit and the register file; detecting, using a buffer full indicator logic, that the writeback buffer is unavailable; transmitting, from the buffer full indicator logic, a buffer unavailable signal in response to detecting the writeback buffer is unavailable; and in response to receiving the buffer unavailable signal at a buffer retrieving logic, writing, using the buffer retrieving logic, the first result from the writeback buffer to the register file.