Virtual Region Mapping
Original Publication Date: 1985-Sep-01
Included in the Prior Art Database: 2005-Feb-19
Providing extended addressability for programs limited to 64K bytes by a 16-bit architecture requires a method of altering the address space definition. Hardware registers called address translation registers (ATRs) control address-space definition. Programs need a generalized mechanism, independent of the physical ATRs, that allows extended addressability without compromising system integrity. Virtual region mapping (VRM) provides a generalized address management facility with: - A single instruction to alter any part or all of the address space. - Multiple distinct storage elements addressable within a single region. - Implicit mapping using transfer of control Supervisor Call (SVC). VRM provides a microcode instruction called the MAP instruction.