Osborne 1

Osborne 1
Osborne 1 open.jpg
Developer Adam Osborne
Release date 1981
Introductory price USD$ 1795
Discontinued 1983
Operating system CP/M
CPU Zilog Z80 at 4.0 MHz
Memory 64 kB

The Osborne 1 was the first commercially successful portable microcomputer, released on April 3, 1981 by Osborne Computer Corporation.[1] It weighed 10.7 kg (23.5lb), cost USD$ 1795,[2] and ran the then-popular CP/M 2.2 operating system. The computer shipped with a large bundle of software that was almost equivalent in value to the machine itself, a practice adopted by other CP/M computer vendors.

Its principal deficiencies were a tiny 5 inches (13 cm) display screen and use of single sided, single density floppy disk drives which could not contain sufficient data for practical business applications.


Market life

The Osborne's design was based largely on the Xerox NoteTaker, a prototype developed at Xerox PARC in 1976 by Alan Kay.[3] The Osborne 1 was developed by Adam Osborne and designed by Lee Felsenstein. It was first announced in April, 1981. Adam Osborne, an author of computer books, decided he wanted to break the price of computers.

The computer was designed to be portable, with a rugged ABS plastic case that closed up and a handle.[4] The Osborne 1 was about the size and weight of a sewing machine and was advertised as the only computer that would fit underneath an airline seat.[2] It is now classified as a "luggable" computer when compared to later laptop designs such as the Epson HX-20.

Despite its unattractive design and heavy weight—it resembled "a cross between a World War II field radio and a shrunken instrument panel of a DC-3",[5] and Felstenstein confessed that carrying two units four blocks to a trade show "nearly pulled my arms out of their sockets"[6]—in the first eight months after April, 1981, when the Osborne 1 was announced, the company sold 11,000 units.[7] Sales at their peak reached 10,000 units per month.[7] In September 1981, Osborne Computer Company had its first US$1 million sales month. Sales of the Osborne 1 were hurt by the company's premature announcement of superior successor machines such as the Osborne Executive,[8] a phenomenon later called the Osborne effect.

From 1982 to 1985 the company published The Portable Companion, a magazine for Osborne users.[9]

Early production

The company initially had ten prototypes produced, as described in an email by Lee Felsenstein, the Osborne 1 designer.[10]

I can confirm that this is one of the first ten prototype units built, known as the "metal case" units. I don't think they had serial numbers. The cases were made by Galgon Industries in Hayward, California but their quote for production was prohibitive, so work immediately commenced on the plastic cases. The circuit board was ready in January of 1981 and these were built shortly thereafter. They were used in the first ads ("the guy on the left doesn't stand a chance") in which the veins on the hand of the guy on the right bulge as he struggles with the 30-pound weight of his transformer-powered luggable. These were the units we took to the West Coast Computer Faire and the National Computer Conference in early 1981.

It weighed 10.7 kilograms (24 lb) and cost USD$1795.[2]


The computer was widely imitated as several other computer companies began offering low-priced portable computers with bundled software. The Osborne's popularity was surpassed by the similar Kaypro II which had a much more practical 9 inches (23 cm) CRT that could display the standard 80 characters on 24 lines as well as double density floppies that could store twice as much data. Osborne Computer Corporation was unable to effectively respond to the Kaypro challenge until after the market window had closed and the day of the 8-bit, CP/M-based computer had ended. IBM had also released new IBM PC, which ran the competitive and increasingly popular DOS operating system.[4] In January 1983 Compaq began shipping the Compaq Portable with a 9 inches (23 cm) CRT. Priced at USD $3590, its software was compatible with the IBM PC, making it an early PC clone.


The Osborne Computer Company announced a successor to the Osborne 1 In 1982, the Executive model OCC-2 and in early 1983, the company announced the more advanced Osborne Vixen,[4] a smaller machine with the keyboard permanently attached, which also acted as a stand. However, unable to beat its competition in the marketplace, Osborne Computer Corporation filed for bankruptcy in September 1983. It released the Osborne-4 (Vixen) in 1985, but it didn't sell in great numbers.


Later model Osborne 1 with the redesigned case

Operating system

The computer ran on the then-popular[2] CP/M 2.2 operating system. A complete listing of the ROM BIOS was available in the Osborne technical manual.[11]

Main memory was eight rows of model 4116 16,384 x 1-bit dynamic RAM chips, shared between CPU memory and video memory. No parity was provided and no provision for memory expansion existed on the motherboard. The boot program loader and significant parts of the BIOS were stored in a 4 kilobyte EPROM, which was bank-switched. A second EPROM was used as a fixed character generator, providing upper and lower case ASCII characters and graphic symbols; the character generator was not accessible to the CPU. The eighth bit of an ASCII character was used to select underlined characters. Serial communications was through a memory-mapped Motorola MC6850 Asynchronous Communications Interface Adapter (ACIA); a jumper on the mother board allowed the MC6850 to be set for either 300 and 1200 baud or 600 and 2400 baud communications, but other bit rates were not available.[11]

The floppy disk drives were interfaced through a Fujitsu 8877 disk controller integrated circuit, a second-source of the Western Digital 1793. The parallel port was connected through a memory-mapped Motorola MC6821 Peripheral Interface Adapter (PIA) which allowed the port to be fully bidirectional; the Osborne manuals also claimed the port implemented the IEEE-488 interface bus but this was rarely used. The parallel port used a card-edge connector etched on the main board, exposed through a hole in the case; any IEEE-488 or printer cable had to be specially manufactured for the Osborne.[11]

The disk drives used either Siemens or MPI full-height single-sided drive mechanisms, but the drive electronics board was replaced by an Osborne-designed board, which allowed both power and signal connections to be carried on the same ribbon cable from the motherboard. The power connections used lines that standard drives reserved for ground.[11]

The video system used part of the main memory and TTL logic to provide video and synch to an internal 5-inch monochrome monitor. The same signals were provided on a card edge connector for an external monitor; both internal and external monitor displayed the same video format.[11]

The processor, memory, floppy controller, PIA, ACIA and EPROMs were interconnected with standard TTL devices.[11]


The Osborne 1 came with a bundle of application software. The WordStar word processor, SuperCalc spreadsheet, and the CBASIC and MBASIC programming languages were the leading applications in their respective niches at the time. The bundle had a retail value of more than USD$1500.[4] The exact contents of the bundled software varied depending on the time of purchase; for example, dBASE II was not included with the first systems sold.

The 500+ page Osborne 1 user manual contained instructions on the hardware, WordStar, Supercalc, BASIC software and the CP/M operating system and utilities
Program Name Version Published by Program Type Date Part Number Number
CBASIC2 Digital Research Language compiler 1979
MBasic Microsoft Language interpreter 301002-02D 1
Colossal Cave Game
Deadline Infocom Game 2
dBase II Ashton-Tate Database
dBase II Tutor Ashton Tate Training for database 6
Nominal Ledger 2.7 PeachTree Software Business Software 1983 2X09200-04 2
Purchase Ledger 2.7 PeachTree Software Business Software 1983 2X09200-04 2
Sales Ledger 2.7 PeachTree Software Business Software 1983 2X09200-04 2
SuperCalc Sorcim Spreadsheet 1981 301002-03 1
Wordstar 2.26 MicroPro Word processor 1


  • Dual 5¼-inch, single-sided 40 track floppy disk drives ("dual density" upgrade available)
  • 4 MHz Z80 CPU
  • 64 kilobytes main memory
  • Fold-down 69 key detachable keyboard doubling as the computer case's lid
  • 5-inch, 52 character × 24 line monochrome CRT display, mapped as a window on 128 × 32 character display memory
  • IEEE-488 port configurable as a Parallel printer port
  • RS-232 compatible 1200 or 300 baud Serial port for use with external modems or serial printers

The Osborne 1 was powered by a wall plug with a switched-mode power supply, and had no internal battery, although an aftermarket battery pack offering 1 hour run-time was available. Early models (tan case) were wired for 120 V or 240 V only.[11] Later models (blue case, shipping after May 1982) could be switched by the user to run on either 120 V or 230 V, 50 or 60 Hz.[11]


Additional peripherals were available by different third-party vendors at various times during the life of the Osborne 1.

  • External Monochrome display. This used separate synchronous and video connections driven by the motherboard video circuitry.
  • Parallel Dot matrix printer. Manufactured by Star
  • 300 baud modem. Fit into a diskette storage pocket and powered from the motherboard.

A small set of aftermarket vendors offered several other upgrades to the basic model, including third-party double density disk drives, external hard disks, and a battery-backed RAM disk that fit in a disk storage compartment.

The Osborne corporation offered a "Screen Pac" 80-column upgrade that could be switched between original 52 column and 80 column modes. Osborne 1 systems with the 80-column upgrade have an RCA jack installed on the front panel to allow users to connect an external composite video monitor.


ADVENT (Colossal Cave Adventure) running on an Osborne Computer circa 1982

Since the display of the Osborne did not support bit-mapped graphics, games were typically character based games, like text adventures (the 1982 game Deadline, for example, packaged in a dossier type folder and came on two 5 1/4" diskettes.). Compiled and MBASIC interpreted versions of Colossal Cave Adventure were available for the Osborne. Some shareware games made good use of the Osborne's limited character-mode graphics.[12]

In popular culture

The Osborne appears briefly in a scene of the movie The Philadelphia Experiment (1984), sitting on a desk inside a USMC base. In the same scene also a Commodore 64 is visible in the foreground.

See also


  1. ^ "First Portable Computer Debuted 30 Years Ago". PC Magazine. http://www.pcmag.com/article2/0,2817,2383022,00.asp. Retrieved 20 April 2011. 
  2. ^ a b c d Fallows, James (July 1982). "Living With a Computer". Atlantic Magazine. http://www.theatlantic.com/doc/198207/fallows-computer/2. Retrieved 21 May 2010. 
  3. ^ "Xerox NoteTaker". Computer History. http://www.computerhistory.org/VirtualVisibleStorage/artifact_main.php?tax_id= Retrieved 21 May 2010. 
  4. ^ a b c d "Osborne 1". OldComputers.net. http://oldcomputers.net/osborne.html. Retrieved 21 May 2010. 
  5. ^ "Computers: Carry Along, Punch In, Read Out". Time (Time Inc.). 1982-06-21. http://www.time.com/time/printout/0,8816,925484,00.html. Retrieved April 3, 2011. 
  6. ^ McCracken, Harry (2011-04-01). "Osborne!". Technologizer. http://technologizer.com/2011/04/01/osborne-computer/. Retrieved April 3, 2011. 
  7. ^ a b Grzanka, Leonard G. (January 1984). Requiem for a Pioneer. Portable Computer. 
  8. ^ Rothman, David H. (1985). The Silicon Jungle. New York: Ballantine Books. p. 33. ISBN 0-345-32063-8. 
  9. ^ "The Portable Companion". http://www.vintage-computer.com/portablecompanion.shtml. Retrieved August 1, 2009. 
  10. ^ Lee Felsenstein (February 12, 2009) (email to PBA Galleries ed.). 
  11. ^ a b c d e f g h Hogan, Thom (1982). Osborne 1 Technical Manual. Mike Iannamico (2F00153-01 ed.). Osborne Computer Corporation. 
  12. ^ Draw Cards Using MBASIC (ISSN 9732-7501 ed.). The Portable Companion. August/September 1982. 

Further reading

  • Adam Osborne, John Dvorak Hypergrowth: the rise and fall of Osborne Computer Corporation, Idthekkethan Pub. Co., 1984 ISBN 0918347009

External links

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