The IBM 4020 Military Computer was a

Cold War The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...

era military computer. Two of them were used in the two IBM AN/FSQ-31 SAC Data Processing Systems. Details: * Instruction rate : Up to 400,000 instructions per second * Cycle time : 2.5 microseconds * Word size : 48 bits + 2 parity bits * Core storage : up to 131,072 words * operates in parallel mode * 69 instructions * single address instructions * Add or subtract : 2.5 microseconds (fixed point) * Add or subtract : (floating point) * Multiply : average 24 μs (24 bit precision fixed point) * Multiply : (floating point) * Multiprocessing with Automatic Priority The instruction format includes: * 7 bit op code * 2 bit real data indicator * 3 bit byte displacement * 3 bit mode selector * 1 sign bit * 8 bit 'byte activity' * 1 bit Double index flag * 1 bit Indirect address flag * 4 bit index register selection * 18 bit address. Man-machine communications included a light-gun to indicate an area of interest on a

visual display unit A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls. Th ...

. Circuit logic packaging was based on 7 types of Q-pacs each holding 1 to 4 circuits. Transistors and semiconductor diodes were soldered to the outside of the Q-pac encapsulation for ease of cooling and replacement.

References

Computer systems of the United States Air Force IBM transistorized computers 48-bit computers {{US-mil-stub, date=May 2014