One embodiment provides a memory controller. The memory controller includes a memory controller memory; a timestamp circuitry and a demarcation voltage (VDM) selection circuitry. The timestamp circuitry is to capture a current timer index from a timer circuitry in response to an initiation of a periodic patrol scrub and to compare the current timer index to a stored timestamp. The VDM selection circuitry is to update a state of a sub-block of a memory array, if the state is less than a threshold and a difference between the current timer index and the stored timestamp is nonzero. The timestamp circuitry is further to store the current timer index as a new timestamp.