Disclosed are a concurrent selftest engine and its applications to verify, initialize and scramble the system memory concurrently along with mainline operations. In prior art, memory reconfiguration and initialization can only be done by firmware with a full system shutdown and reboot. The disclosed hardware, working along with firmware, allows us to do comprehensive memory test operations on the extended customer memory area while the customer mainline memory accesses arc running in parallel. The hardware consists of concurrent selftest engines and priority logic. Great flexibility is achieved by the new design because customer-usable memory area can be dynamically allocated, verified and initialized. The system performance is improved by the fact that the selftest is hardware-driven whereas in prior art, the firmware drove the selftest. More comprehensive test patterns can be used to improve system memory RAS as well.