The IBM 4020 Military Computer was a

Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...

era military computer. Two of them were used in the two

IBM AN/FSQ-31 SAC Data Processing System The IBM AN/FSQ-31 SAC Data Processing System (FSQ-31, Q-31, colloq.) was a USAF command, control, and coordination system for the Cold War Strategic Air Command (SAC). IBM's Federal Systems Division was the prime contractor for the AN/FSQ-31s, ...

s. 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. 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

IBM transistorized computers Military electronics of the United States 48-bit computers {{US-mil-stub, date=May 2014