A method of controlling access to a model specific register of a microprocessor. A method of controlling access to a model specific register of a processor having a normal execution mode and a secure execution mode may include storing processor state and mode information in the model specific register. Further, the method may include protection logic allowing a software invoked write access to modify the information within the model specific register during the normal execution mode. The method may further include security logic selectively inhibiting the software invoked write access during the secure execution mode.