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David B. Tuttle, Principal Engineer  
Profile, Projects, Activities


MIT Logo MIT Computation Center
Building 26 & Building 32
Massachusetts Institute of Technology
77 Massachusetts Avenue, Cambridge, MA

When I started at MIT in the Fall of 1966, there were two large computer systems and a variety of smaller machines, frequently experimental, scattered in laboratory spaces around the campus.

The IBM 7094 on the first floor of Building 26 was, at that time, the main processing facility for the university.  It was a unique machine modified for MIT by IBM, running the Compatible Time Sharing System (CTSS) developed at MIT in the early 1960's.  CTSS provided interactive terminal access for online users and interleaved conventional batch jobs on a machine-time-available basis.

In the basement corridor below the main 7094 system there were several rooms of IBM punched card equiment - 026 and 029 keypunch, 059 verifier, 083 card sorter, 407 tabulating printer, etc.  There was also an IBM 1401 system (perhaps two; I'm not entirely sure) with high-speed card readers, line printers, and tape drives.  As was common practice at that time, the 1401 system was used to copy user-submitted card decks onto magnetic tape for later submission to the upstairs batch system, then to print output and/or punch cards from the tapes generated during the batch operations.

On the second floor of Building 26 there were some additional machines, notably the TX-0 system that had been built as a prototype of the later Digital Equipment Corp. products.

Past the main machine room on the first floor, the corridor continued into a passageway with the World War II era Radiation Laboratory (Building 24) off to the right and Building 32 (a converted garage, reportedly) off to the left.  Building 32 housed the IBM System/360 Model 65 and several offices for the Computation Center staff.

Notable projects & activities:

User Support Consultant (part-time) – February 1967 - May 1967

  • Online user of MIT Compatible Time Sharing System (CTSS) on modified IBM 7094
  • Unit record operations on IBM 1401, 026/027 keypunch, 1403 printer, etc.
  • System/360 Programming in FORTRAN IV, PL/1 and System/360 Assembly
  • Enhanced CTSS '21' Blackjack game in Michigan Algorithm Decoder (MAD)
  • Fortran SLIP library (list processing) updated to S/360 Fortran IV

System Programmer – Summer 1967

  • OS/360-PCP Sysgen and installation on System/360 Model 65
  • Installation and extensive customization of IBM Attached Support Processor (ASP) software with System/360 Model 40 channel-attached to System/360 Model 65
  • OS/360 I/O device programming, Job Control Language and utility programming
  • 'Spacewar' video game experience on IBM 2250 Model 1 vector graphics display

The IBM ASP software provided, for the System/360 system, a function similar to that provided for CTSS by the IBM 1401 system.  Since time on the large machines was a scarce resource, it made economic sense to use less expensive systems for reading input cards, punching card output, and printing hard-copy results.

Toward the end of 1967, I think, MIT exchanged the early-model System/360-65 CPU for an updated version with extended microcode support.  The new machine was capable of running either System/360 programs or, in emulation mode, programs written for the IBM 7094.  The ASP front end software recognized when an input job required the 7094 emulator instead of native S/360 operation, allowing it to switch the main processor between modes automatically.

User Support Consultant (part time) – Fall 1967 - Spring 1968

  • SHARE Software Librarian for MITCC
  • System Installation and Utility programming on IBM System/360 model 20
  • Assembly-language rewrite of Fortran three-space coordinate transformation functions, supporting molecular structure analysis of stereoisomers


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This page last updated on  24-Feb-2013.