User opt-in processor feature control capability

A processor includes a feature control unit to enable or disable one or more processor features individually in response to a user selectable setting. The feature control unit is adapted to disable the processor feature(s) if the user setting has not been updated in accordance with an input regardless of the value of the user setting prior to the update and to enable or disable the processor feature(s) in accordance with the updated user setting after it has been updated. The feature control unit may also include a lock unit to prevent changes to the updated user setting and a software feature selection unit to enable or disable processor features in response to a software feature selection setting and, optionally, only enable or disable processor features whose corresponding updated user setting is user enabled. The feature control unit may also include mechanisms to detect illegal feature selection conditions.