Abstract: The virtual memory managing system of the present invention includes a virtual memory managing unit that manages a virtual memory system by combining swap-out in page units and swap-out in task units. The virtual memory managing unit includes: a memory area reserving unit that creates and manages swap management tables corresponding to a memory area reserve requests from tasks and reserves memory areas for the memory area reserve requests; a swap-out control unit that, when swap-out becomes necessary, determines whether swap-out should be carried out in page units or batch swap-out should be carried out in task units, and based on this determination, controls swap-out and sets information in the swap management tables; and a swap-out object limiting means that, when batch swap-out is to be carried out in task units, carries out a limited swap-out based on the swap management tables.

Abstract: An input/output (I/O) buffer has a block-end detector which detects that an access has reached the last word in a block of the I/O buffer. If the block-end detector detects the last word of the block, then the block is invalidated. The I/O buffer also has a direct-memory-access-end detector which detects that an access has reached the last word in a direct-memory-access (DMA) transfer. If the DMA-end detector detects the last word of the DMA transfer, then the block is invalidated. The I/O buffer may also have a configuration memory which stores configuration information concerning whether a DMA controller accesses the input/output buffer instead of a storage. If the configuration information indicates that the DMA controller does not access the input/output buffer, then data from the storage are bypassed to the DMA controller.