Instructions providing new functionality for utilization by a target system program of host system container words during computer system emulation with host word size larger than that of the emulated machine

摘要

Two unique instructions for the instruction set of a target 36-bit machine which is emulated on a host 64-bit machine are provided in order to achieve visibility, to an emulated application program, of a “containing” word stored in the memory of the host machine. A “LOAD64” instruction loads the emulator memory location representing an emulated “Q” (supplementary accumulator) register with the “normal” 36-bits of the containing word. At the same time, the “upper” 28 bits of the 64-bit containing word is copied into the emulator memory location representing an emulated “A” (accumulator) register. Thus, the emulated 36-bit machine “sees” and can examine the 64-bit word in its entirety. A “Store64” instruction stores the emulated “Q” register contents into the lower 36-bits of the 64-bit containing word, and at the same time stores the lower 28 bits of the emulated “A” register contents into the upper 28 bits of the 64-bit containing word.