Quantum chemical calculations using the floating point systems, Inc. Model 164 attached processor

The Theoretical Chemistry Group at Argonne National Laboratory has had a Floating Point System, Inc., Model 164 Attached Processor (FPS‐164) for several months. Actual production calculations, as well as benchmark calculations, indicate that the FPS‐164 is capable of performance comparable to large mainframe computers. Our experience with the FPS‐164 includes the conversion of a complete system of electronic structure codes, including integral evaluation programs, generalized valence bond programs, integral transformation programs, and unitary group configuration interaction programs, and two classical trajectory codes. Timings of these programs at various levels of optimization along with estimates of the amount of effort required to make the necessary program modifications are discussed.