The Placement of Computer Logic Modules

Abstract

The object of the work described was to develop a procedure for the allocation of logic to cards, boards, platters and so on which utilize modular circuit design and etched wiring techniques. A chain of logic elements is a set of interconnected (logic) elements two of which connect to, at least, the remaining elements of this set. Every logic diagram has a characteristic set of chains. A subset of these chains is selected to initiate the determination of the locations of each element on a card. The elements of a chain are assigned to one row or column of platter locations. The positions of the chains in relation to one another are determined by such criteria as total wire length reduction, proximity requirements between gates based on electrical considerations and the proximity requirements between elements and pins based on timing considerations. The effectiveness of the automatic procedure was tested during the design of small cards (mounting 16 modules, up to 64 gates). In these circumstances human experience and insight are at their best. The layouts of experienced technicians and engineers were compared with the layouts produced by the program. Significant similarities between the determinations were found in all cases tested.