A non-volatile random access memory (NVRAM) is used in a computer system to provide instant responses to sleep state transitions. The computer system includes a processor coupled to an NVRAM, which is accessible by the processor without passing through an I/O subsystem. The NVRAM is byte-rewritable and byte-erasable by the processor. In response to a request to enter a powered sleep state, the computer system converts the powered sleep state into a powered-off sleep state with system memory context stored in the NVRAM. The powered sleep state is defined as a state in which power is supplied to volatile random access memory in the computer system, and the powered-off sleep state is defined as a state in which power is removed from the volatile random access memory. In response to a wake event, the computer system resumes working state operations using the system memory context stored in the NVRAM.