The methods for fine-grained power management of physical system memory allow portions of the system volatile memory to be independently power managed. The system volatile memory may be partitioned into a plurality of power management units (PMUs). Each PMU may have a pre-determined size or a variable size, which may be less than the size of a memory chip. Each PMU may be placed in a different memory state and independently power managed according to the memory state. At opportune times during the system active state, a fractional potion of the system volatile memory is shadowed into the system nonvolatile memory. Active data in the system volatile memory is rearranged prior to entering a power-saving mode and the PMUs containing the shadowed data may be powered off. Thus, power efficiency of the system volatile memory is improved.