1. An apparatus for stack pointer comparison comprising: a first register means for storing a stack pointer value; a second register means for storing a stack pointer base value; a comparison means, coupled to the first register means and the second register means, for producing an equivalence signal on a positive comparison of equivalence between the stack pointer value and the stack pointer base value; a storage means, coupled to the comparison means, for storing the equivalence signal; an instruction storage means for storing an instruction and producing an instruction signal when a stack memory retrieval instruction is stored; a logic combining means, coupled to the storage means and the instruction storage means, for combining the equivalence signal with the instruction signal and producing a stack exception signal upon receiving an assertive logic level in both the equivalence signal and the instruction signal; and a condition-flag storage means, coupled to the logic combining means, for storing the stack exception signal and producing an exception signal upon receiving the stack exception signal.