page_title: Apollo Guidance Computer
section_title: Design
hierarchical_section_title: Apollo Guidance Computer / Design
caption_attribution_description: Deutsch: AGC Flatpack (Block II) Quelle: NASA (pd)
context_page_description: The Apollo Guidance Computer is a digital computer produced for the Apollo program that was installed on board each Apollo command module and Apollo Lunar Module. The AGC provided computation and electronic interfaces for guidance, navigation, and control of the spacecraft.
  The AGC has a 16-bit word length, with 15 data bits and one parity bit. Most of the software on the AGC is stored in a special read-only memory known as core rope memory, fashioned by weaving wires through and around magnetic cores, though a small amount of read/write core memory is available.
  Astronauts communicated with the AGC using a numeric display and keyboard called the DSKY. The AGC and its DSKY user interface were developed in the early 1960s for the Apollo program by the MIT Instrumentation Laboratory and first flew in 1966. The AGC was the first silicon integrated circuit based computer. The computer's performance was comparable to the first generation of home computers from the late 1970s, such as the Apple II, TRS-80, and Commodore PET.
context_section_description: The AGC was designed at the MIT Instrumentation Laboratory under Charles Stark Draper, with hardware design led by Eldon C. Hall. Early architectural work came from J.H. Laning Jr., Albert Hopkins, Richard Battin, Ramon Alonso, and Hugh Blair-Smith.
  The flight hardware was fabricated by Raytheon, whose Herb Thaler was also on the architectural team.
  Following the use of integrated circuit (IC) chips in the Interplanetary Monitoring Platform (IMP) in 1963, IC technology was later adopted for the AGC. The Apollo flight computer was the first computer to use silicon IC chips.
  While the Block I version used 4,100 ICs, each containing a single three-input NOR gate, the later Block II version (used in the crewed flights) used 2,800 ICs, each with dual three-input NOR gates. The ICs, from Fairchild Semiconductor, were implemented using resistor–transistor logic (RTL) in a flat-pack. They were connected via wire wrap, and the wiring was then embedded in cast epoxy plastic. The use of a single type of IC (the dual NOR3) throughout the AGC avoided problems that plagued another early IC computer design, the Minuteman II guidance computer, which used a mix of diode–transistor logic and diode logic gates. This is possible because NOR gates are universal logic gates from which any other gate can be made, though at the cost of using more gates.
  The computer had 2048 words of erasable magnetic-core memory and 36 kilowords of read-only core rope memory. Both had cycle times of 11.72 microseconds. The memory word length was 16 bits: 15 bits of data and one odd-parity bit. The CPU-internal 16-bit word format was 14 bits of data, one overflow bit, and one sign bit (ones' complement representation).
caption: Flatpack silicon integrated circuits in the Apollo guidance computer
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