Atlas Computer

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Atlas Architecture

The Architecture

The main parts of Atlas 1 consist of:-

  1. The control unit: responsible for pipelined instruction decoding and initiating the relevant action
  2. Floating Point Arithmetic Unit: for all floating point arithmetic operations
  3. Integer Arithmetic Unit: for all integer and character operations
  4. The Supervisor: schedules the running of jobs and switching as necessary. Atlas was probably the first machine whose control program warranted being called an operating system.
  5. The storage system: programs could address a million words of store which either resided in main memory or on drums. The Supervisor made this appear like a 1-level storage system by paging blocks of information in and out of main store.
  6. Input and output devices: the main backing store was either 1 inch Ampex pre-formatted tape or a fixed disc. Compatible IBM 7-track magnetic tape decks were also available.

The following diagram shows the component parts of Atlas 1:-

INPUT V-STORE OUTPUT FIXED STORE SUPERVISOR AND SUPERVISOR WORKING SPACE SYSTEM MAGNETIC TAPE PRIVATE STORES CONTROL B-REGISTERS B-REGISTERS ARITHMETIC UNIT ACCUMULATOR ACCUMULATOR ARITHMETIC UNIT MAGNETIC DRUMS CORE STORE MAGNETIC Tape GENERAL STORES