Patent US 5,649,142

A method and apparatus for translating a first address in a first address space, such as a processor address space, to a second address in a second address space, such as system address space, and for accessing a service routine in response to a page fault, are described. In one embodiment, the apparatus for translating comprises a processor; a page table having a translation mask register, a comparison value register, and a replacement value register; and a comparator coupled to the comparison value register and to the replacement value register. A programmable mask within the translation mask register is employed to partition a virtual address. A first subaddress comprises a subset of the bits of the first address and a second subaddress comprises remaining bits of the first address. The first subaddress is masked with a programmable mask value in the translation mask register and is compared by the comparator with successive values in the comparison value register until a match comparison value is found. If a match comparison value is found, a programmable replacement value in the replacement value register corresponding to the match comparison value is concatenated with the second subaddress to provide the second address. If a match comparison value is not found, a fault interrupt is generated to interrupt the translation and the processor accesses a service routine in accordance with the fault interrupt.