Purchase of an Array Processor to Enhance Quantum Chemistry Calculations.

Abstract : The original proposal was to add an array processor to the VAX 11/750, previously purchased with a DOD grant, in order to increase the throughput by a factor of five. However, after extensive comparative studies of array processors and stand-alone computers, it was concluded that none of the available array processors in the accessible price range were sufficiently reliable and that the desired factor of five increase in speed might not be achieved. Therefore, the alternative of trading in the VAX 11/750 on a new stand-alone computer was considered as an alternative. Benchmark tests were developed using the program GAMESS, and these benchmarks combined with known reliability led us to purchase a VAX 8530, manufactured by Digital Equipment Corporation. This computer, configured with 16 megabytes of real memory, 1.35 gigabytes of disk space, a tape drive, a printer, and a console, provides us with approximately six times the throughput of the 8530, thereby exceeding our expectations.