A method of an aspect, which may be performed responsive to one or more structure access instructions, includes changing a state of a portion of a structure of a processor to a sequestered state. In the sequestered state, components of the processor are not able to access the portion of the structure but are able to access one or more other portions of the structure. Non-architecturally visible data in the portion of the structure is modified, while the portion of the structure is in the sequestered state. The state of the portion of the structure is then changed from the sequestered state to a non-sequestered state, after the non-architecturally visible data in the portion of the structure has been modified. Other methods, apparatus, systems, and instructions are also disclosed.
