Other more speculative memory systems include magnetoresistive random-access memory (MRAM) and phase-change memory (PRAM). MRAM is based on a grid of magnetic tunnel junctions. MRAM's reads the memory using the tunnel magnetoresistance effect, allowing it to read the memory both non-destructively and with very little power. Early MRAM used field induced writing, reached a limit in terms of size, which kept it much larger than flash devices. However, new MRAM techniques might overcome the size limitation to make MRAM competitive even with flash memory. The techniques are Thermal Assisted Switching (TAS), developed by Crocus Technology, and Spin-transfer torque on which Crocus, Hynix, IBM, and other companies were working in 2009.