A computer implemented method in a processor to perform a backing store switch from a first context (source context) to a second context (target context) is provided whereby the backing store memory image and RSE will be synchronized with the processor's execution of instructions. The processor includes a register stack (RS) device that includes a portion allocated for dirty registers. The portion is defined by first and second physical register numbers. The processor further includes a register stack engine (RSE) to exchange information in one of an instruction execution dependent and independent modes between a storage area and the RS. The processor further includes a FLUSHRS state machine to notify the RSE to store dirty register in the RS to a backing store located in a memory.