In some embodiments, a system comprises a system memory module and an access card. The system memory module connects to a memory bus on a motherboard for a personal computer, while the access card connects to an expansion bus. The access card couples to the system memory module to provide power when the personal computer is unpowered. When the personal computer boots, the system memory module operates in a cloaked mode that hides the system memory module from a memory bus. The access card switches the system memory module from the cloaked mode to a normal mode in response to a command received via the expansion bus. For long-term power outages, the access card may copy data from the system memory module to a nonvolatile information storage device. Energy storage and nonvolatile information storage may be provided by a separate longevity unit that couples to the access card.