1. A method comprising: receiving soft information regarding a codeword at an iterative low density parity check (“LDPC”) decoder, by a decoder unit, that operates according to a parity check matrix arranged as a plurality of ordered rows each corresponding to a parity constraint; performing updates of the soft information at the iterative decoder for a particular iteration by processing the ordered rows sequentially, each consecutive parity constraint of an ordered row being updated sequentially one parity constraint at a time using results based on previous parity constraint updates of the particular iteration; and converging on the codeword after the particular iteration.