Burroughs MCP
Collage of stills from Burroughs 16mm films, 1962-4. Source: Youtube @slurn45.
Like IBM, Burroughs was a company originally formed in the 19th century to produce mechanical calculators and accounting machines. By the late 1950s it had built several small computers such as the B220 and also worked on the system for controlling the Atlas ICBM. But it had no large civilian system such as IBM's 7090 on offer.
This did give one advantage: a blank sheet of paper to design a new system. This yielded several innovations:
- The ability to design the hardware and operating system in parallel, rather than add software after the computer had been designed.
- It was programmed in high level languages only - the system language was an extension of Algol - and had no assembler.
- It had A stack driven architecture and virtual memory.
The system the came up with was the B5000 which ran an batch operating system called the MCP, or Master Control Program. Introduced in 1963, its first customers included NASA, Dow Chemicals, Stanford University and Georgia Tech. However, it only sold 33 systems by the end of 1964, with concerns over performance and the lack of a Fortran compiler; it was also overshadowed by the launch of IBM's System/360 in 1964.
Later that year Burroughs announced the B5500. Using integrated circuits instead of transistors, and a disk drive instead of a drum, it was almost 3 times faster. A Fortran compiler was added, along with data communication equipment. These supported remote entry of batch jobs and interaction with programs. However, MCP was tuned for fast throughput of long running jobs, keeping a few in memory and queuing the rest, so latency for interactive use was not great.
The solution was to add full time-sharing, which it did with the TSSMCP in 1968. This ran a shell called CANDE (Command & Edit) on up to 24 terminals, providing an interactive environment reminiscent of DTSS where users could develop and run programs in Algol, BASIC, Fortran and COBOL. An early customer for time-sharing was the UK's GPO, which used it for telephone network analysis.
Its ease of programming and flexibility helped in the market, with 220 B5500s sold by 1970. Burroughs would continue to develop the system and the MCP, but was always overshadowed by IBM. It merged with another IBM rival, Sperry, in 1986 to form Unisys. MCP continues to be supported by Unisys today, now via (paid) emulation on x86 hardware.
Preservation status
For software, there are some listings on bitsavers but the most important artefact is a complete copy of the Mark XIII (1971) release of MCP, found on a 7 track tape in the collection of Sid McHarg. This was concerted by Paul Pierce to a tape file and Unisys has allowed this to be distributed under a non-commercial use license. You can find it on Paul Kimpel's site. There is also a collection of miscellaneous software including the CUBE tapes, which was a user-contributed library of programs from Burroughs users.
For documentation, bitsavers has a good collection of manuals for the hardware, operating system and languages.
Emulation status
There are two excellent Burroughs B5500 emulators that take quite different approaches.
Paul Kimpel and Nigel Williams developed retro-b5500. This is written in Javascript and runs in the browser, storing virtual disk files in the browser's local files. It has a user interface that presents each system component - console, printer, tape drive etc - in a form similar to the original hardware, so you get a great idea of how the machine was operated. It runs the batch and time-sharing MCP, though the latter is limited to a single terminal. The documentation is complete and well written; the story of how the project was built is also a fascinating read.
The prolific Richard Cornwell has developed a version of simh for the architecture. This uses the traditional command line interface, supports multiple terminals and brings the automation features of simh which can help with some tasks. Richard's project page contains full information about setting up and using the system; the quick start guide is a good place to start.
I believe Unisys used to offer Windows emulators of its contemporary MCP product under a hobbyist license, but the links I have no longer work.
Further reading
The Wikipedia articles on Burroughs and its large systems are good places to start.
The IEEE Annals of the History of Computers articles "Before the B5000" and "After the B5000" give a detailed history of Burroughs computers around this period.
There are several good oral histories about this period. Richard Waychoff's Stories about the B5000 (pdf; archive.org link) gives an account of the development of the Algol compiler, with a cameo from a young Donald Knith. The B5000 Conference brings together many of the people involved in the system's design to discuss its origins.
Topics
These will be covered in future posts.
- A quickstart guide to retro-b6600
- A quickstart guide to simh
- MCP Architecture
- Using CANDE
- Batch and the operator's console
- Getting data in and out
- Programming: BASIC, Algol, Fortran and COBOL
Questions, corrections, comments
I welcome any questions or comments, and also especially any corrections if I have got something wrong. Please email me at rupert@timereshared.com and I will add it here and update the main text.