A data processing system is arranged to execute multiple program threads, with each program thread comprising program thread instructions. An interpreter is operable, during execution of each program thread, to employ a table pointer to reference a table to determine for a current program thread instruction a sequence of native instructions to be executed by the processor core to effect execution of that current program thread instruction. A consistency module is provided which is responsive to occurrence of a predetermined event to cause the table pointer to be manipulated, such that for a predetermined number of the program threads, the interpreter will be operable to associate a subsequent program thread instruction with a predetermined routine to be executed by the processor core, the predetermined routine being operable to cause the state of the corresponding program thread to be made available for subsequent reference.