Enabling this option restricts the use of all memory locations (memory and peripherals) not explicitly defined by the isolation setup. In a secure system this would typically be checked, however, there are operations in a system that are not always clear and could be impacted by this parameter. For example, when loading authenticated and/or encrypted images after boot (a partial bit file), the system must access the CSU, eFuse, and potentially BBRAM register space. If these are not explicitly added to the secure subsystem performing this action, it will be blocked by the lock unused memory option. For more details see Isolation Methods in ZynqUltraScale+MPSoCs (XAPP1320) [Ref 38].