A computer system comprises a processor, a memory module and input/output devices. The memory module includes a circuit board, a volatile memory unit mounted on the circuit board, a non-volatile memory unit mounted on the circuit board and a control circuit mounted on the circuit board. The volatile memory unit comprises DRAM devices, and the non-volatile memory unit comprises flash memory. The processor is configured to execute an operating system (OS) and an application program and to present a memory address space to the application program. The memory address space including a memory mapped input/output (MMIO) space mapped to the I/O devices, a pseudo MMIO (PMMIO) space mapped to the non-volatile memory unit, and a DRAM space mapped to the volatile memory unit, the PMMIO space including a system main memory local storage (MMLS) area and a memory channel storage area, wherein the DRAM space is partitioned into memory pages, and the MCS space is partitioned into storage blocks.