The invention relates to a method for processing instructions out-of-order on a processor comprising an arrangement of execution units. The inventive method comprises looking up operand sources in a Register Positioning Table and setting operand input references of the instruction to be issued accordingly, checking for an Execution Unit (EXU) available for receiving a new instruction, and issuing the instruction to the available Execution Unit and entering a reference of the result register addressed by the instruction to be issued to the Execution Unit into the Register Positioning Table (RPT).