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 secondCycle time : 2.5 microsecondsWord size : 48 bits + 2 parity bitsCore storage : up to 131,072 wordsoperates in parallel mode69 instructionssingle address instructionsAdd or subtract : 2.5 microseconds (fixed point)Add or subtract : 7.7 to 26 µs (floating point)Multiply : average 24 µs (24 bit precision fixed point)Multiply : 5 to 74 µs (floating point)Multiprocessing with Automatic PriorityThe instruction format includes:
7 bit op code2 bit real data indicator3 bit byte displacement3 bit mode selector1 sign bit8 bit 'byte activity'1 bit Double index flag1 bit Indirect address flag4 bit index register selection18 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.
