Abstract: A method for executing a non-native mode-sensitive instruction within a computer system is disclosed. In accordance with the method and system of the present invention, a computer system as described, capable of executing a non-native mode-sensitive instruction, includes a system memory, an instruction set convertor, and a processor. The system memory is utilized to store the non-native mode-sensitive instruction. The instruction set convertor, having a Semantics Table, is utilized for converting the non-native mode-sensitive instruction to a group of native instructions by preemptively testing whether or not the mode-sensitive instruction is preceded by a mode-altering instruction within a single block, and for accessing the Semantics Table for the non-native instruction with an address according to the preemptive testing. The processor is then utilized to process the group of native instructions from the instruction set convertor.