only does it retain its memory with the power turned off but also there is no constant power-draw. While the read process in theory requires more power than the same process in a DRAM, in practice the difference appears to be very close to zero. However, the write process requires more power to overcome the existing field stored in the junction, varying from three to eight times the power required during reading. Although the exact amount of power savings depends on the nature of the work — more frequent writing will require more power – in general MRAM proponents expect much lower power consumption (up to 99% less) compared to DRAM. STT-based MRAMs eliminate the difference between reading and writing, further reducing power requirements. It is also worth comparing MRAM with another common memory system — flash RAM. Like MRAM, flash does not lose its memory when power is removed, which makes it very common in applications requiring persistent storage. When used for reading, flash and MRAM are very similar in power requirements. However, flash is re-written using a large pulse of voltage (about 10 V) that is stored up over time in a charge pump, which is both power-hungry and time-consuming. In addition, the current pulse physically degrades the flash cells, which means flash can only be written to some finite number of times before it must be replaced. In contrast, MRAM requires only slightly more power to write than read, and no change in the voltage, eliminating the need for a charge pump. This leads to much faster operation, lower power consumption, and an indefinitely long lifetime. Data retention MRAM is often touted as being a non-volatile memory. However, the current mainstream high-capacity MRAM, spin-transfer torque memory, provides improved retention at the cost of higher power consumption, i.e., higher write current. In particular, the critical (minimum) write current is directly proportional to the thermal stability factor Δ. The retention is in turn proportional to exp(Δ). The retention, therefore, degrades exponentially with reduced write current. Speed Dynamic random-access memory (DRAM) performance is limited by the rate at which the charge stored in the cells can be drained (for reading) or stored (for writing). MRAM operation is based on measuring voltages rather than charges or currents, so there is less "settling time" needed. IBM researchers have demonstrated MRAM devices with access times on the order of 2 ns, somewhat better