catflap.org Online Dictionary Query

  IBM 704
       
           A large, scientific computer made by IBM and used
          by the largest commercial, government and educational
          institutions.
       
          The IBM 704 had 36-bit memory words, 15-bit addresses and
          instructions with one address.  A few index register
          instructions had the infamous 15-bit decrement field in
          addition to the 15-bit address.
       
          The 704, and IBM 709 which had the same basic architecture,
          represented a substantial step forward from the IBM 650's
          magnetic drum storage as they provided random access at
          electronic speed to core storage, typically 32k words of 36
          bits each.
       
          [Or did the 704 actually come *before* the 650?]
       
          A typical 700 series installation would be in a specially
          built room of perhaps 1000 to 2000 square feet, with cables
          running under a raised floor and substantial air conditioning.
          There might be up to eight magnetic tape transports, each
          about 3 x 3 x 6 feet, on one or two "channels."  The 1/2 inch
          tape had seven tracks and moved at 150 inches per second,
          giving a read/write speed of 15,000 six bit characters (plus
          parity) per second.
       
          In the centre would be the operator's console consisting of
          cabinets and tables for storage of tapes and boxes of cards;
          and a card reader, a card punch, and a line printer,
          each perhaps 4 x 4 x 5 feet in dimension.  Small jobs could
          be entered via punched cards at the console, but as a rule
          the user jobs were transferred from cards to magnetic tape
          by off-line equipment and only control information was
          entered at the console (see SPOOL).  Before each job, the
          operating system was loaded from a read-only system tape
          (because the system in core could have been corrupted by the
          previous user), and then the user's program, in the form of
          card images on the input tape, would be run.  Program output
          would be written to another tape (typically on another
          channel) for printing off-line.
       
          Well run installations would transfer the user's cards to
          tape, run the job, and print the output tape with a turnaround
          time of one to four hours.
       
          The processing unit typically occupied a position symmetric
          but opposite the operator's console.  Physically the largest
          of the units, it included a glass enclosure a few feet in
          dimension in which could be seen the "core" about one foot on
          each side.  The 36-bit word could hold two 18-bit addresses
          called the "Contents of the Address Register" ({CAR) and the
          "Contents of the Decrement Register" ({CDR).
       
          On the opposite side of the floor from the tape drives and
          operator's console would be a desk and bookshelves for the
          ever-present (24 hours a day) "field engineer" dressed in, you
          guessed it, a grey flannel suit and tie.  The maintenance of
          the many thousands of vacuum tubes, each with limited
          lifetime, and the cleaning, lubrication, and adjustment of
          mechanical equipment, was augmented by a constant flow of
          bug reports, change orders to both hardware and software,
          and hand-holding for worried users.
       
          The 704 was oriented toward scientific work and included
          floating point hardware and the first Fortran
          implementation.  Its hardware was the basis for the
          requirement in some programming languages that loops must be
          executed at least once.
       
          The IBM 705 was the business counterpart of the 704.  The
          705 was a decimal machine with a circular register which could
          hold several variables (numbers, values) at the same time.
       
          Very few 700 series computers remained in service by 1965, but
          the IBM 7090, using transistors but similar in logical
          structure, remained an important machine until the production
          of the earliest integrated circuits.
       
          [Was the 704 scientific, business or general purpose?
          Difference between 704 and 709?]
       
          (1996-01-24)