Abstract: 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.

Abstract: The cache keeps regularly accessed disk I/O data within RAM that forms part of a computer systems main memory. The cache operates across a network of computers systems, maintaining cache coherency for the disk I/O devices that are shared by the multiple computer systems within that network. Read access for disk I/O data that is contained within the RAM is returned much faster than would occur if the disk I/O device was accessed directly. The data is held in one of three areas of the RAM for the cache, dependent on the size of the I/O access. The total RAM containing the three areas for the cache does not occupy a fixed amount of a computers main memory. The RAM for the cache grows to contain more disk I/O data on demand and shrinks when more of the main memory is required by the computer system for other uses.