To improve the write performance of PCM, the disclosed technology, in certain embodiments, provides a new write scheme, referred to herein as two-stage-write, which leverages the speed and power asymmetries of writing a zero bit and a one bit. Writing a data block to PCM is divided into two separated stages, i.e., write-0 stage and write-1 stage. Without violating power constraints, during the write-0 stage, all zero bits in this data block are written to PCM at an accelerated speed; during the write-1 stage, all one bits are written to PCM, with more bits being written concurrently. In certain embodiments, the disclosed technology provides a new coding scheme to improve the speed of the write-1 stage by further increasing the number of bits that can be written to PCM in parallel.