With the advent of high-speed computers having large memory capacities, it has become possible to automate one of the more difficult and time-consuming areas of computer developmental work; namely, that of checking the logical design. This paper describes one such method which utilizes an IBM 704 to simulate the logical equivalent of a specific computer under development by Nortronics Division of Northrop Corporation. Such logic testing before fabrication and checkout of the first computer eliminates much of the expensive checkout time usually required. The method employed by this simulation technique can readily be adapted to other types of digital equipment.