The Community for Technology Leaders
RSS Icon
Issue No.01 - Jan.-March (2013 vol.35)
pp: 23-34
Arne Martin Fevolden , Nordic Institute for Studies in Innovation, Research, and Education
This account of the evolution of time-shared microcomputers, often overlooked members of the microcomputer industry, looks at articles and advertisements that appeared in Byte magazine from 1977 to 1983. The author's quantitative and qualitative analysis reveals that time-shared microcomputers attempted to combine the best aspects of microcomputer and mini-computer/mainframe technologies and, for a time, were a considerable, important part of the microcomputer industry.
Microcomputers, Companies, Time sharing computer systems, History, Industries, microcomputer and computer industry, history of computing, time-sharing
Arne Martin Fevolden, "The Best of Both Worlds? A History of Time-Shared Microcomputers, 1977–1983", IEEE Annals of the History of Computing, vol.35, no. 1, pp. 23-34, Jan.-March 2013, doi:10.1109/MAHC.2012.36
1. P.E. Ceruzzi, A History of Modern Computing, MIT Press, 2000, p. 263
2. The term microcomputer will in this article refer to the microprocessor-based systems that appeared in the mid-1970s to early 1980s and not microprocessor-based workstations or mini-computers that became popular later.
3. Two notable exceptions are R.X. Cringely, Accidental Empires: How the Boys of Silicon Valley Make Their Millions, Battle Foreign Competition, and Still Can't Get a Date, HarperCollins, 1996, and P. Freiberger and M. Swaine, Fire in the Valley: The Making of the Personal Computer, 2nd ed., McGraw-Hill, 2000.
4. See S.B. Bassett, "Taking on the Minis: The Beginning of a Revolution," InfoWorld,31 Mar. 1980, pp. 14, 18.
5. See advertisement in Byte, Aug. 1977, p. 25.
6. A likely candidate for the first company to introduce a time-shared microcomputer is the French company Réalisation d'Études Électroniques (R2E). In 1973, R2E introduced the first microcomputer, Micral, which it soon after turned into a multiuser system. Nevertheless, it is difficult to find sufficient information about the hardware, software, and the employment of these multiuser systems to conclude decisively on whether they constituted the first time-shared microcomputers and when they first appeared.
7. See articles in industry magazines such as A. Rosenberg, "Time-Sharing: A Status Report – Problems and Prospects," Datamation, Feb. 1966, pp. 66–77, and R.A. Colilla, "Time-Sharing and Multiprocessing Terminology: Toward Standardized Usage," Datamation, Mar. 1966, pp. 49–51, and technical literature such as D.F. Parkhill, The Challenge of the Computer Utility, Addison-Wesley, 1966.
8. Rosenberg, "Time-Sharing: A Status Report − Problems and Prospects," Datamation.
9. See E. Pugh, Building IBM, MIT Press, 1995, chap. 15; and C.J. Bashe et al., IBM's Early Computers, MIT Press, 1986,, chaps. 7 and 12.
10. A.L. Norberg and J.E. O'Neill, Transforming Computer Technology: Information Processing for the Pentagon, 1962–1986, Johns Hopkins Univ. Press, 1996, chap. 2. For an interesting account of the development of these systems in the financial sector, see B. Bátiz-Lazo, J.C. Maixé-Altés, and P. Thomes eds., Technological Innovation in Retail Finance: International Historical Perspectives, Routledge, 2010.
11. J.E. O'Neill,, "The Evolution of Interactive Computing Through Time-Sharing and Networking," doctoral dissertation, Univ. of Minnesota, 1992, chap. 3.
12. M. Campbell-Kelly and D.D. Carcia-Swartz, "Economic Perspectives on the History of the Computer Time-Sharing Industry, 1965–1985," IEEE Annals of the History of Computing, vol. 30, no. 1, 2008, pp. 16–36; and Norberg and O'Neill, Transforming Computer Technology, chap. 2.
13. T. Jackson, Inside Intel: Andy Grove and the Rise of the World's Most Powerful Chip Company, Dutton Adult, 1997, chap. 8; and J. Zygmont, Microchip: An Idea, Its Genesis, and the Revolution It Created, Persues Publishing, 2003, chap. 9.
14. Ceruzzi, A History of Modern Computing, pp. 226–241.
15. J.W. Cortada, Information Technology as Business History: Issues in the History and Management of Computers, Greenwood Press, 1996, p. 168.
16. N. Gandal, S. Greenstein, and D. Salant, "Adoptions and Orphans in the Early Microcomputer Market," J. Industrial Economics, vol. 47, no. 1, 1999, pp. 87–105.
17. The mini-computers could often be spotted by looking at information about the processing unit, which would not advertise a recognizable microprocessor brand. The microcomputers with only a common hard drive could often be identified by comparing how many simultaneous users they could support compared to "true" time-shared microcomputer systems, which relied on similar hardware. The shared hard-drive systems could support far more users because each users were allocated their own microprocessor.
18. See for instance Ceruzzi, A History of Modern Computing; and L. Heide, "Retail Banking and the Dynamics of Information Technology in Business Organizations," B. Bátiz-Lazo, J.C. Maixé-Altés, and P. Thomes eds., Technological Innovation in Retail Finance, Routledge, 2011.
19. The companies offering time-shared microcomputers are for reasons of clarity described in this article as "time-shared microcomputer companies," even though many (or most) of them also offered single-user systems.
20. See statistics in R.N. Langlois,, "External Economies and Economic Progress: the Case of the Microcomputer Industry," Business History Rev., vol. 66, Spring 1992, pp. 1–50.
21. It is a truism in advertising that you pay for increased visibility. I am unaware of the actual rates that Byte charged. They were likely negotiable and varied with demand.
22. E.K. Yasaki, "Microcomputers: For Fun and Profit?" Datamation, vol. 23, no. 7, July 1977, pp. 66–71.
23. J.L. McKenney, D.C. Copeland, and R.O. Mason, Waves of Change: Business Evolution Through Information Technology, Harvard Business School Press, 1995, pp. 16–17, found that the microprocessors had at least a five to six times better price/performance ratio than the processors used by the mini-computers and mainframes. Nevertheless, it is difficult to make a direct and complete comparison of microcomputers and mini-computers and mainframes because the mini-computers and mainframes were in many other ways more sophisticated than the microcomputers, as the article in Datamation also points out.
24. Jackson, Inside Intel, pp. 74–76; and Zygmont, Microchip, chap. 9.
25. Zilog's Z-80 were used, among others, in Cromemco's systems ( Byte, June 1978, p. 1; Byte, Nov. 1981, p. 3); Motorola's 6800 and 6502 were used, among others, in Ohio Scientific's system ( Byte, Aug. 1978, p. 22; Byte, Sept. 1980, inside back cover); and Intel's 8086 were used, among others, in Techmar's systems ( Byte, June 1982, p. 383 ). All these processors were also used in single-user microcomputer systems (see E. Braun and S. Macdonald, Revolution in Miniature: The History and Impact of Semiconductor Electronics, Cambridge Univ. Press, 1982 ).
26. Most single-user and time-shared microcomputer companies adopted the S-100 motherboard standard, which must have ensured at least a certain level of cross-compatibility of peripherals and RAM: Ceruzzi, A History of Modern Computing, chap. 7.
27. Both Altos and Ohio Scientific's systems used Winchester hard disks (see, for instance, Byte, Aug. 1978, p. 22, and Byte, Aug. 1981, p. 89 ), which was also popular brand among mini-computer and mainframe companies ( Ceruzzi, A History of Modern Computing, p. 200).
28. For instance, Extensys Corporation had its own multiuser operating system called EMOS ( Byte, Apr. 1978, p. 5), Cromemco had the Cromemco Multi-User Operating System ( Byte, Aug. 1978, p. 1), and Ohio Scientific's systems came with a whole library of applications software for small business users ( Byte, Feb. 1979, inside back cover). See also discussion about proprietary operating systems in Bassett, "Taking on the Minis," InfoWorld.
29. Digital Research first advertised its multiuser operating system, MP/M, in Byte, Oct. 1979, p. 217. See also G.A. Kildall, "CP/M: A Family of 8- and 16-Bit Operating Systems," Byte, vol. 6, no. 6, June 1981, pp. 216–231. Other companies apart from Digital Research also introduced multiuser operating systems for different types of computers, such as Administrative Systems, which introduced a multiuser operating system called Tempos ( Byte, Mar. 1979, p. 127 ), and Microsoft, which introduced a multiuser operating system call Xenix ( R.B. Greenberg, "The Unix Operating System and the Xenix Standard Operating Environment," Byte, vol. 6, no. 6, June 1981, pp. 248–264 ). Both Digital Research and Administrative Systems claimed in their advertisement that their operating systems were quickly becoming the new standard for time-shared microcomputers.
30. Altos ( Byte, Aug. 1980, p. 148 ) and Industrial Micro Systems ( Byte, Oct. 1980, p. 39 ), for instance, introduced systems that were compatible with the multiuser CP/M and other independent multiuser operating systems.
31. See discussion in T. Hogan, "Share and Share Alike: Mulituser Hardware Explained," InfoWorld, vol. 3, no. 11, 8 June 1981, pp. 18–19.
32. See discussion in Hogan, "Share and Share Alike," InfoWorld, and Williams, "Two Current Approaches: Taking Stock of Multiuser Systems," InfoWorld,17 Mar. 1980, pp. 15, 23.
33. See, for instance, Byte, Aug. 1978, p. 22; and Byte, Sept. 1980, inside back cover.
34. T. Williams, "Two Current Approaches," InfoWorld; and T. Hogan, "Altos Multiple-User System," InfoWorld,8 June 1981, pp. 44–46.
35. Some of the semiconductor companies such as Intel introduced processors (such as Intel's 80286) that were specifically designed for time-sharing ( Cringely, Accidental Empires, pp. 176–177).
36. See, for instance, ads by Ohio Scientific in Byte, Nov. 1977, pp. 42–43.
37. Bassett, "Taking on the Minis," InfoWorld.
38. Technical systems consultants and Cromemco, among others, introduced a special-purpose time-sharing system that provided access to the programming language Basic (see Byte, Aug. 1977, p. 25, and Byte, Mar. 1979, p. 1 ). General-purpose time-sharing seems to have become common from 1980 onward.
39. See Bassett, "Taking on the Minis," InfoWorld, and A. Lundell, "Timesharing," InfoWorld,8 June 1981, pp. 16–17.
40. See advertisement by Cromemco in Byte, Dec. 1980, p. 1.
41. See S. Linker, "Time-Sharing: Squeezing the Most from Your Micro," Byte, June 1979, pp. 228–233; Yasaki, "Microcomputers: For Fun and Profit?" Datamation, 1977; Bassett, "Taking on the Minis," InfoWorld; and W.L. Frank, "Micros and Software Architecture," Computerworld,10 Aug. 1981, pp. 35, 37.
42. See A.D. Chandler, Inventing the Electronic Century: The Epic Story of the Consumer Electronics and Computer Industries, Free Press, 2001, pp. 138–139, and Langlois, "External Economies and Economic Progress," p. 23.
43. Cringely, Accidental Empires, pp. 128–130, 164.
44. M. Campbell-Kelly, From Airline Reservations to Sonic the Hedgehog: A History of the Software Industry, MIT Press, 2003, pp. 240–242.
45. Campbell-Kelly, From Airline Reservations to Sonic the Hedgehog, chap. 8.
46. Another possible explanation (inspired by J. Appelquist, "Technical and Organizational Change in Swedish Banking," B. Bátiz-Lazo, J.C. Maixé-Altés, and P. Thomes eds., Technological Innovation in Retail Finance, Routledge, 2011, ) is that management ideologies affect computer architecture and that time-sharing lost popularity because of changes in organizational structures.
47. See Williams, "Two Current Approaches," InfoWorld; and Frank, "Micros and Software Architecture," Computerworld.
21 ms
(Ver 2.0)

Marketing Automation Platform Marketing Automation Tool