History of CP/CMS - Historical Notes

Historical Notes

The following notes provide brief quotes, primarily from Pugh and Varian, illustrating the development context of CP/CMS. Direct quotes rather than paraphrases are provided here, because the authors' perspectives color their interpretations.

• Early time-sharing and CTSS: Early papers on time-sharing started to appear around 1959. CTSS was the seminal system that "taught the world how to do time-sharing." It was first demonstrated at MIT in 1961, on an IBM 709, and was in production use from 1964-1974. Programmers were Marjorie Merwin-Daggett, Robert Daley, Robert Creasy, Jessica Hellwig, Richard Orenstein (later a cofounder of National CSS), and Lyndalee Korn, all working under Professor Fernando Corbató. MIT developers asked for and received considerable assistance from IBM in making hardware modifications to facilitate CTSS processing. Creasy describes the important influence of CTSS on CP/CMS: "CTSS… most strongly influenced the CP/CMS system design.… provided a subset of the machine for use by normal batch programs… run without modification as with a normal system. The time-sharing supervisor would steal and restore the machine without their knowledge. This technique was extended to its fullest in CP/CMS. Many other CTSS design elements and system facilities, like the user interface, terminal control, disk file system, and attachment of other computers, served as operational prototypes.… The necessity of compatibility for evolutionary growth of software was demonstrated by CTSS; for hardware, by the IBM System/360 family."

• Role of John McCarthy (of LISP fame) in timesharing: "At about this time John McCarthy… gave a special evening lecture ended on the speculative note that computation might eventually 'be organized as a public utility, just as the telephone system is a public utility.' This insightful prediction can be seen to anticipate the role of the Internet. Similar sentiments were later expressed forcefully by Alan Kay and others. IBM leadership had a very different view of computation.

• IBM and MIT: IBM’s president T.J. Watson "had very shrewdly given" MIT an IBM 704 for use by MIT and other New England schools, beginning what was to be a very close relationship. IBM established an MIT Liaison Office, housed at the MIT Computation Center, staffing it with skilled technicians. Watson recalls that he "went up to MIT in 1955 and urged them to start training computer scientists.… a very aggressive college discount program… within five years there was a whole new generation of computer scientists who made it possible for the market to boom." Varian adds the following interesting footnote: "It appears that (without a clear directive from Corporate management) IBM’s Cambridge Branch Office decided to interpret Watson’s original grant to MIT as authorization for them to upgrade the system at MIT whenever IBM produced a more powerful computer."

• Project MAC and MULTICS: MIT's Project MAC was launched in 1963 to build a new time-sharing system following in the footsteps of CTSS. IBM submitted a bid to provide a modified S/360 with address translation (the "Blaauw Box"), which was also bid to Bell Labs around the same time. MIT and Bell Labs both chose another vendor. This had "important consequences for IBM. Seldom after that would IBM processors be the machines of choice for leading-edge academic computer science research." MULTICS and UNIX (plus various other minicomputer platforms) became the de facto research systems.

• MIT input to S/360: IBM personnel with close ties to MIT became "strong proponents of time-sharing" and kept System/360 designers aware of work at MIT, including the purpose of the CTSS hardware enhancements. System/360 architects visited MIT and talked with Professor Corbató. Nevertheless, the IBM belief was now that "time-sharing would never amount to anything and that what the world needed was faster batch processing." When the System/360 was announced in 1964 without address relocation, MIT and other time-sharing advocates felt betrayed.

• Virtual memory and timesharing: "In June ... adamant that hardware-aided dynamic address translation (DAT) was essential" for time-sharing, a "still-experimental mode of operation whereby users at several consoles could share the facilities of a computer.... The most fundamental problem....was that of reallocating memory areas to user programs dynamically." MIT wouldn't back down on this position, felt betrayed by IBM, and ultimiately turned away from IBM to GE for a MULTICS platform.

• Cambridge Scientific Center (CSC): Established in 1964 by Norm Rasmussen, in the same building with Project MAC (a location with "ten or fifteen time-sharing systems being coded or tested or accessed" in the mid 60s), CSC developed and maintained close ties with MIT researchers. "All of IBM’s contractual relationships with MIT were turned over to the new Scientific Center to administer." After losing Project MAC, the team unexpectedly had nothing to do. This was the environment where CP-40 came to life.

• Two competing strategies at IBM in 1964: IBM engineers were divided over the right technical path for the company:
  • "Unifying the architecture and control programs of business and scientific computers both large and small" (championed by Brooks/Amdahl; this group rejected dynamic address translation, fearing "unevaluated techniques or technologies" as the basis of an entire product line), versus
  • Changing "the way computing power was meted out in universities and laboratories" (i.e. timesharing, championed by MIT researchers working closely with IBM).

• Divided opinion about the S/360: CSC staff became champions of the System/360 architecture, in the face of deep skepticism in the scientific community. Creasy notes: "The family concept of the IBM System/360… was a most amazing turning point in computer development, one which was not universally greeted with enthusiasm. We believed that the architecture of System/360, combining scientific and commercial instruction sets, would be around for a significant period of time. the trauma associated with widespread recoding of programs also pointed to a long life. In addition, we speculated that many operating systems and a large number of application programs would be produced over the lifetime of that machine design." These proved to be good predictions.

• IBM's 1965 reorganization: The two IBM product divisions pursuing time-sharing development — Advanced Systems Development Division (ASDD) and Data Systems Division (DSD) — were "phased out; their… resources were assigned to the new Systems Development Division (SDD)… and the new Systems Manufacturing Division ." The disbanding of large organizations previously responsible for time-sharing efforts suggests the political forces at work.

• 360/67 and TSS: Rasmussen felt betrayed by IBM's decision to ignore time-sharing, and he decided "that the Cambridge Scientific Center would write a time-sharing system for System/360." The loss of Project MAC had finally attracted attention within IBM, and resources were made available to help "win bids for time-sharing systems." Rough specifications were prepared for the new S/360-67, which would incorporate address translation (via the "DAT Box", which unlike the "Blaauw Box", supported both segment and page tables) and a new operating system: TSS. "A group of six sites… had a non-disclosure agreement" during the system's development (probably Lincoln Lab, University of Michigan, Carnegie University, Bell Labs, General Motors, and Union Carbide). The University of Michigan and MIT's Lincoln Laboratory were two of the first sales, and had a role in the hardware design. TSS was announced in August 1965, an "elegant and very ambitious system" but "snatched from its nest too young" with "serious stability and performance problems."

• CSC financial resources: Rasmussen used creative accounting to fund the creation of CP-40. Varian: "When IBM gave the 7094 to the MIT Computation Center, it retained the night shift on that machine for its own use. So, because the Scientific Center had inherited IBM’s contracts with MIT, Rasmussen 'owned' eight hours of 7094 time per day. He traded part of that time to the Computation Center for CTSS time for his programmers to use in doing their development work. He 'sold' the remainder to IBM hardware developers in Poughkeepsie, who badly needed 7094 time to run a design automation program that was critical for System/360 hardware development. With the internal funds he acquired this way, he paid for the modifications to the Model 40… part-time employees, mainly MIT students, and to pay the salaries of IBMers who came to Cambridge to work on the system… 'unbudgeted revenues'...to keep a very low profile." Rasmussen also sold spare time on another, temporary S/360-40, provided by IBM to CSC while they waited for their modified virtual memory system. If there was a perception at MIT that MIT funds went into CP/CMS, it may have come from these complicated transactions. Of course, regardless of funding issues, researchers from outside IBM, especially from MIT and Union Carbide, clearly made direct and indirect contributions. This also would have clouded perceptions of authorship.

• Anti-timesharing decisions: "During 1961 and 1962 time-sharing close contact with the MIT Computation Center through sales and special engineering personnel." After MIT's criticisms, and their ultimate choice of GE for MULTICS, an IBM task force "made useful suggestions but effectively endorsed the work of the 360 designers by reporting that too little was known about the time-sharing mode of operation to justify .… In 1967, an industry observer counted about forty general-purpose time-sharing installations in the United States – up from ten in 1965 and up from one (the MIT demonstration) in 1961. Some of the cost of development was being offset by a research agency in the Department of Defense, which sponsored six of the first dozen."

• Informal release of CP/CMS: CP-67/CMS "was announced informally because it was developed outside of the product development organizations in the product and marketing divisions. See IBM Installation Newsletter 68-10, 31 May 1968, 'New Type III Programs,' pp. 13–5." Note that this description does not mention company politics, the possible use of public funds, the role of Lincoln Labs, etc.

• Relationship of early time-sharing to introduction of HP-35: Before the availability of powerful handheld calculators in 1972, during the "first decade of time-sharing, one use for a terminal was to request minor calculations that needed to be carried to more decimal places than possible with a slide rule." This was one reason time-sharing was so important to scientific and academic users.

• Virtual memory, and IBM's fear of risk: "In the aftermath of the System/360 trauma," a reference to large-project woes such as those described by Fred Brooks, IBM executives "took steps to ensure that the company would never again become committed to such a high-risk program." At the height of this loin-girding is when timesharing and virtual memory were shunted aside by IBM, in favor of mainstream commercial batch processing. It is ironic that, by 1970-71, other forces within IBM "set in motion an effort to create the Future System (FS) technological objectives at least as risky as those of System/360.… Three and a half years later, the project was abandoned." It is well known that Gene Amdahl, a key FS player, continued to pursue FS objectives and technologies after leaving IBM.

• Intent and use of CP/CMS: Creasy provides this fascinating insight: "CMS was developed… to support its own development and maintenance… maintain the other components of VM/370.… In most cases, a subset of features was selected with the expectation of future work. We expected many operating systems to flourish in the virtual machine environment. What better place for experimentation with new system ideas? This has not been the case. Instead, many features were added to CMS to extend its usage into areas better served by new systems." A generation later, as we face a diversity of platforms built in the collaborative open source world, it is easy to understand Creasy's hopes for CP/CMS as a development incubator, and his disappointment in what must have seemed missed opportunities. This has been the fate of many research systems, but few share the 40+ year arc of the concepts launched with CP-40.