The IBM System/360 Model 91: Floating-Point Execution Unit
by S. F. Anderson, J. G. Earle, R. E. Goldschmidt, D. M. Powers
The principal requirement for the Model 91 floating-point execution unit was that it be designed to support the instruction-issuing rate of the processor. The chosen solution was to develop separate, instruction-oriented algorithms for the add, multiply, and divide functions. Linked together by the floating-point instruction unit, the multiple execution units provide concurrent instruction execution at the burst rate of one instruction per cycle.