IBM System/360 Model 91

IBM System/360 Model 91

System/360 Model 91 Panel at the Goddard Space Flight Center
Developer	IBM
Release date	January 1966
Predecessor	IBM 7090
Successor	IBM S/360 Model 195

The IBM System/360 Model 91 was announced in 1964 as a competitor to the CDC 6600.^[1] Functionally, the Model 91 ran like any other large-scale System/360, but the internal organization was the most advanced of the System/360 line, and it was the first IBM computer to support out-of-order instruction execution.^[2] It ran OS/360 as its operating system. It was designed to handle high-speed data processing for scientific applications. This included space exploration, theoretical astronomy, sub-atomic physics and global weather forecasting.^[3]

The first Model 91 was used at the NASA Goddard Space Flight Center in 1968 and at the time was the most powerful computer in user operation. It was capable of executing up to 16.6 million instructions per second,^[3] making it roughly equivalent to an Intel 80486SX-20 MHz CPU or AMD 80386DX-40 MHz CPU in MIPS performance.

The CPU consisted of five autonomous units: instruction, floating-point, fixed-point, and two storage controllers for the overlapping memory units and the I/O data channels. The floating-point unit made heavy use of instruction pipelining^[4] and was the first implementation of Tomasulo's algorithm.^{[citation needed]} It was also one of the first computers to utilize multi-channel memory architecture.

Castells-Rufas et al. reported that the 360/91 used 74kW of power.^[5]