DONUT: A Threshold Gate Computer

During the past few years there has been a considerable amount of literature concerned with the realization of threshold logic. However, there are a number of questions concerning such factors as sensitivity and component savings which cannot be completely answered by such theoretical studies. DONUT (Digitally Operated Network Using Thresholds) is a small general purpose digital computer which was designed and constructed to evaluate the feasibility of using threshold gates as the basic logical element. Exclusive of memory the computer consists of about 500 threshold gates. The design was carried out for five different values of component tolerances and the tightest tolerance version was constructed. Component savings for the constructed machine are about a factor of four compared with the loosest tolerance NOR gate realization. Experiments were made to verify that the power supply and logical voltages were within tolerances in the system environment.