PERFORMANCE 543

performance indicator compared to the conventional, but poor, instruction rate measure. For more unconventional machines, instructions per second tends to become a significantly poorer measure. The various vector/array machines (e.g., ILLIAC IV, CDC STAR. CRAY-I) have single instructions to operate on at least 64 operands per instruction; hence instructions per second would be a poor measure. Hand-held calculators have single instructions such as Sin, Polar-to-Cartesian coordinate conversion; using anything but a final benchmark problem would be unfair. Accesses per second used here are as a processor performance measure.

Figure 1. Basic PMS computer structure model with six relevant performance/structure dimensions.