ACCESS CONTROL SYSTEM FOR EXTENDED MEMORY DEVICE

摘要

PURPOSE:To reduce overhead by allocating a logical address similar to that of a main memory device also to the area of an extended memory device and carrying out an instruction after converting the address of a prescribed operand into a real address of the extended memory device. CONSTITUTION:An address conversion table group 26 consists of the tables showing the correspondence between a logical address and a real page 10 of a main memory 2 and between a logical address and a real page 30 of an extended memory device 3. An instruction executing part 21 delivers a prescribed one of two operand addresses to an access control part 22 as a logical address for conversion into a real address of the memory 2 with the other operand address as a logical address for conversion into a real address of the memory 3 respectively when a specific instruction is processed. Then the part 21 gives accesses to both memories 2 and 3 via a main memory control part 13 and an extended memory control part respectively and carries out the processes decided by a data transfer instruction and other instructions. Thus it is possible to give an access only to an allocated area of the memory 3 and therefore to eliminate the overhead caused by intervention of a control program.