MICROPROCESSOR INCLUDING MULTIPLE REGISTER FILES MAPPED TO THE SAME LOGICAL STORAGE AND INHIBITING SYNCHRONIZATION BETWEEN THE REGISTER FILES RESPONSIVE TO INCLUSION OF AN INSTRUCTION IN AN INSTRUCTION SEQUENCE

A microprocessor includes a first register file including a plurality of multimedia registers defined to store operands for multimedia instructions and a second register file including a plurality of floating point registers defined to store operands for floating point instructions. The multimedia registers and floating point registers are mapped to the same logical storage according to the instruction set employed by the microprocessor. In order to maintain predefined behavior when a floating point instruction reads a register most recently updated by a multimedia instruction or vice versa, the microprocessor provides for synchronization of the first and second register files between executing a set of one or more multimedia instructions and a set of one or more floating point instructions (where either set may be prior to the other in program order and the order affects which direction copying of the contents is performed, i.e. first register file to second register file or vice versa). The predefined behavior in the above mentioned circumstances is thereby maintained. The microprocessor supports an empty state instruction. If the empty state instruction is included between the set of one or more multimedia instructions and the set of one or more floating point instructions in a code sequence, the microprocessor inhibits the register file synchronization. In one embodiment including the x86 instruction set, the empty state instruction performs the same set of actions as the EMMS instruction in addition to the above mentioned features.