Method and apparatus for selective writing of incoherent MMX registers

A dual register file MMX-type architecture comprises monitoring logic for identifying which registers in a register file have been written to. The monitoring logic is coupled to write-enable logic associated with each register. Detection logic indicates the occurrence of an instruction boundary event and asserts a signal indicating the possibility of data incoherence between the register files. Control logic coupled to the register files cause a transfer of data between the two register files in response to the asserted signal. The monitoring logic acts in conjunction with the write-enable logic to disable write operations to the receiving registers when the corresponding transferring registers have not been written to.