Abstract: A computer system operable as a virtual machine system capable of accessing multiple virtual address spaces, which has an access register translation means for translating a space identifier into an origin address of a table for address translation and a translation pair memory for storing translation pairs of the space identifiers and the associated origin addresses. In each entry of the translation pair memory, a field is provided in association with the translation pair, for storing a machine identifier of the guest virtual machine associated with the translation pair. When accessing a virtual address space, a guest virtual machine makes reference only to the associated translation pair based on the virtual machine identifier thereof.

Abstract: Instead of translation from a space address to a segment table origin address (STO) by an ordinary instruction, translation to the STO is done by a space base register modify instruction which uses an instruction to modify the content of the space register, and the result thereof is used for the operand address calculation of the instruction to the operand data fetching. The present system eliminates the need for additionally providing for hardware of an operand fetch unit hardware for the translation from the space address to the STO, memory for storing translation pairs of the space addresses and the STO's and the table look-up of the translation pairs. Thus, degradation of performance is minimized with less hardware.