Multilevel differential sensing in phase change memory

A multi-differential multi-bit phase change memory comprising:

• a plurality of multi-bit phase change memory cells organized in groups of n>2 co-addressed physical cells, cells within ones of said groups each having a different one of n possible states such that each group of cells can have n factorial (n!) possible collective states, such that when the address corresponding to a particular group is received, the physical cells within said particular group are collectively accessed, so that each cell in said particular group provides an output when said particular group is read;
• and
• one or more multi-differential multi-bit sense amplifiers which compare multiple pairs of respective outputs from respective ones of said physical cells within an accessed one of said groups,
• wherein said sense amplifiers accordingly provide output bits which indicate corresponding nonvolatile states of said multiple physical cells within said respective group.