Computer systems design and analysis through simulation

In March 1965, the Lockheed Missiles & Space Company's Computation Center installed a UNIVAC 1107 with two FH880 drums and three UNIVAC 1004 print, card punch and read systems, two of which are remote. This configuration is illustrated in Fig. 1. The Central Processing Unit was scheduled to be upgraded to an 1108 in October 1965. The UNIVAC EXEC II monitor was used for the operating control of this equipment. Under this monitor, the typical job enters the system through a 1004 card reader, queues at a section of one drum designated the Input/Output buffer, is processed by the main frame using the drums for scratch storage and systems routines, occupies I/O drum buffer area for storage of output, and is printed on the originating 1004 system. The monitor "steals" cycles from the main frame to control the flow of data between the 1004's and the drum I/O buffer. The insert in Fig. 1 shows the original storage allocation of the two FH880 drums which allocated 262,000 36-bit words to the I/O buffer.