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CPMulator
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<p>CPMulator is a program to emulate the <a href="/facts/CP%2fM/n5rTgXdC">CP/M</a> operating system under x86 <a href="/facts/DOS/sWwDXNmX">DOS</a>. The program was developed in 1984 by Keystone Software Development. The company was owned and operated by Jay Sprenkle. </p><p>The <a href="/facts/NEC_V20/gUVUbklA">NEC V20</a> processor released that year was guaranteed to be hardware compatible with the <a href="/facts/Intel_8088/DdWKfyBp">Intel 8088</a>. After reviewing the instruction timing of the math operations and instruction addressing hardware it was determined it could slightly speed up existing 8088 based <a href="/facts/IBM_PC/yhcJGMPL">IBM PC</a> machines. Keystone software started advertising "PC Speedup Kits" in <i><a href="/facts/PCWeek/qNe5TdLW">PCWeek</a></i> magazine. The CPU was socketed in IBM PC's so it could easily be replaced. In practice most programs received a 5% speed increase but those that were math intensive were much improved. One customer reported his <a href="/facts/Monte_carlo_simulation/AkHjY7jc">monte carlo simulation</a> of a nuclear reactor was so much faster that he "double checked the results because he couldn't believe it was finished." </p><p>CPMulator was developed after the release of the V20. The processor was also able to emulate the <a href="/facts/Intel_8080/32FvNTcD">Intel 8080</a> instruction set in hardware. This opened the possibility of running older code on the new IBM machines. CPMulator was designed to modify CP/M binaries to make them run as if native 8088 DOS programs. The code to put the CPU in emulation mode was prefixed to each CP/M executable. Any calls to the CP/M operating system were intercepted and translated to DOS operating system calls. The program would leave 8080 emulation mode, make the operating system call, translate the results to CP/M standards and returned to emulation mode and continue the original program. </p><p>The product went out of production after <a href="/facts/IBM_AT/YEVHpWKF">AT</a> class machines became prevalent and NEC produced no V series pin for pin compatible version of <a href="/facts/80286/rucEU93g">80286</a> processor. </p>