In this paper, we review recent progress made in ultra-low power computing system with non-volatile magnetic random access memory (MRAM). Compared with the traditional Spin Transfer Torque (STT) based memories, Spin Orbit Torque (SOT) mechanism offers higher write speed, lower power consumption, and potentially infinite endurance. In particular, Spin-Hall assisted STT achieves a purely electrical operation in absence of an external magnetic field, and opens the door to real normally-off/instant-on computing with non-volatility at all levels of the memory hierarchy.