The IBM 4020 Military Computer was a Cold War 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.
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.
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