Osborne 1

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Osborne 1
Osborne 1 open.jpg
DeveloperAdam Osborne
TypePortable computer
Release dateApril 3, 1981; 37 years ago (1981-04-03)
Introductory priceUS$1,795 (equivalent to $4,832 in 2017)
Discontinued1983 (1983)
Operating systemCP/M
CPUZilog Z80 @ 4.0 MHz
Memory64 KB RAM
SuccessorOsborne Executive

The Osborne 1 was the first commercially successful portable microcomputer, released on April 3, 1981, by Osborne Computer Corporation. It weighed 10.7 kg (24.5 lb), cost US$1,795, and ran the CP/M 2.2 operating system. Powered directly from a mains socket as it had no on-board battery, it was still classed as a portable device since it could be hand-carried when packed.

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 at the time.

Competitors such as the Kaypro II that used double density drives and had a larger 9" screen which could display 80×25 text quickly appeared.


The Osborne 1 was developed by Adam Osborne and designed by Lee Felsenstein. It was first announced in early 1981. Osborne, an author of computer books, decided he wanted to break the price of computers.

The Osborne's design was based largely on the Xerox NoteTaker, a prototype developed at Xerox PARC in 1976 by Alan Kay.[1] The computer was designed to be portable, with a rugged ABS plastic case that closed up, and a handle.[2] 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.[3] 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—the Osborne 1 was described as resembling "a cross between a World War II field radio and a shrunken instrument panel of a DC-3",[4] and Felstenstein confessed that carrying two units four blocks to a trade show "nearly pulled my arms out of their sockets"[5]—the computer amazed observers. BYTE wrote, "(1) it will cost $1795, and (2) it's portable!"[6] ($1795 is the equivalent of $4832 today.) The bundled word processing, spreadsheet, and other software alone was worth $1,500; as InfoWorld stated in an April 1981 front-page article on the new computer after listing the included software, "In case you think the price printed above was a mistake, we'll repeat it: $1795."[7][8]

Osborne claimed that the new computer had a "significant price/performance advantage" but emphasized the price, stating that its performance was "merely adequate": "It is not the fastest microcomputer, it doesn't have huge amounts of disk storage space, and it is not especially expandable."[7] Beyond the price, advertisements emphasized the computer's portability and bundled software.[9] In the first eight months after April 1981, when the Osborne 1 was announced, the company sold 11,000 units.[10] Sales at their peak reached 10,000 units per month.[10]

Its principal deficiencies were a tiny 5-inch (13 cm) display screen and use of single sided, single density floppy disk drives which could not contain sufficient data for practical business applications, and considerable unit weight. Adam Osborne decided to use single-sided disk drives out of concern about double-sided drives suffering head damage from rough handling. A single-density disk controller was used to keep costs down. As a result, the Osborne's floppy disks held a mere 90k.

Later Osborne models switched to double-density controllers and an upgrade was offered to owners of the original model Osborne 1.

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,[11] a phenomenon later called the Osborne effect.

From 1982 to 1985, the company published The Portable Companion, a magazine for Osborne users.[12]

Early production[edit]

The company initially had ten prototypes produced, as described in an email by Lee Felsenstein, the Osborne 1 designer.[13]

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 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.


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.

In 1981, IBM released the 16-bit IBM PC which was significantly more powerful and expandable than 8-bit computers of the day.[2] Following the release of the IBM-compatible Compaq Portable in 1983, the market for CP/M computers quickly plummeted and Osborne was unable to compete.


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.[2] This was a smaller machine with the keyboard permanently attached and serving 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 did not sell in great numbers.


Later model Osborne 1 with the redesigned case

The 64 KB main memory was made of four rows of eight type 4116 dynamic RAM chips, each with 16,384 bits. Memory was shared, with 60 KB available for software and 4 KB reserved for 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 motherboard 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.[14]

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.[14]

The diskette drives installed in the Osborne 1 were Siemens FDD 100-5s (MPI drives were also used later), which were actually manufactured in California by GSI, a drive manufacturer that the German firm had purchased. They utilized a custom controller board that Osborne produced themselves, which among other things had a single connector for both the power and data lines. The FDD 100-5 proved to be quite trouble-prone as Osborne's quality control was lacking and many of the controller boards had soldering defects. In addition, the drive cable was not keyed and could be very easily installed upside-down, which would short out components in the computer and there were also problems with the drive head going past track 0 and getting stuck in place. The combo power/data cable also had a tendency of overheating.[14]

The video system used part of the main memory and TTL logic to provide video and sync 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.[14]

The processor, memory, floppy controller, PIA, ACIA and EPROMs were interconnected with standard TTL devices.[14]

The Osborne 1 had bank switched memory. Unusually for a system based on the Z80, all I/O was memory mapped, and the Z80 I/O instructions were only used to select memory banks. Bank 1 was "normal" mode, where user programs ran; this included a 4 kB area at the top of the address space which was video memory. Bank 2 was called "shadow". The first 4 kB of this address space was the ROM, and 4 kB was reserved for the on-board I/O ports. These were the disk controller, the keyboard, the parallel port PIA, the serial port ACIA, and a second PIA chip used for the video system. All memory above the first 16 KB was the same memory as Bank 1. This was the mode of the system on power up, because this was where the boot ROM was mapped. Bank 3 had only 4 kb by 1 bit of memory, used solely to hold the "dim" attribute of the video system.

Operating system[edit]

The computer ran on the then-popular[3] CP/M 2.2 operating system. A complete listing of the ROM BIOS was available in the Osborne technical manual.[14]


The 500+ page Osborne 1 user manual contained instructions on the hardware, WordStar, Supercalc, BASIC software and the CP/M operating system and utilities

The Osborne 1 came with a bundle of application software with a retail value of more than US$1500, including the WordStar word processor, SuperCalc spreadsheet, and the CBASIC and MBASIC programming languages.[8] 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.

Program Name Version Published by Program Type Date Part Number Number
CP/M 2.2 Digital Research Disk Operating System
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


The Osborne 1 was powered by a wall plug with a switched-mode power supply, and had no internal battery. An aftermarket battery pack offering 1-hour run-time was available, and connected to the system through a front panel socket. Early models (tan case) were wired for 120 V or 240 V only.[14] 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.[14] There was no internal fan; a hatch at the top of the (blue) case could be opened for ventilation.


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 monochrome synch 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" column upgrade that could be switched between original 52 column, 80 column and 104 column modes. Osborne 1 systems with the Screen-Pac upgrade have an RCA jack installed on the front panel to allow users to connect an external composite video monitor. [15] This modification was developed in Australia by Geoff Cohen and Stuart Ritchie and taken to the US by Stuart who turned up unannounced and sat outside Adam Osborne's office for two days. Osborne bought the mod as soon as they saw it and both of them worked with the Company to implement the mod. As a nod toward where it came from it was called the "Koala Project". Geoff went on to invent many other upgrades for Osborne's and was regarded as the Australian expert on the computers.


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

Since, like most CP/M systems, the display of the Osborne did not support bit-mapped graphics, games were typically character based games, like Hamurabi or text adventures (the 1982 game Deadline, for example, packaged in a dossier type folder and came on two 5​14" diskettes.). Compiled and MBASIC interpreted versions of Colossal Cave Adventure were available for the Osborne. Some type in games made good use of the Osborne's limited character-mode graphics.[16]


Jerry Pournelle wrote that the small size of the Osborne's screen surprised him by not being a problem, and stated that after using it at Caltech when Voyager 1 arrived at Saturn, "a dozen science writers were ready to go buy an Osborne 1". He added, "I was able to type ... without disrupting the meeting at all. The Osborne 1 is quiet and efficient and not at all distracting ... You can't beat it for the price, under $2000 bucks with over a thousand dollars' worth of software. An Osborne and an Epson printer will put you in the computing/word-processing business cheaper than anything I can think of".[17] BYTE stated "If you need a solid, well-supported, well-documented business system at a reasonable price, you should give [the Osborne 1] a great deal of consideration". The reviewer calculated that after subtracting $1530 for the retail price of the bundled software the price of the computer was "only $265 ... in a way you are getting a software package with a computer thrown in for (almost) free". He praised the quality of the documentation, and agreed with Pournelle that the screen's size did not cause difficulty.[8] Freelance journalist David Kline praised the Osborne 1's durability, reporting in 1982 that the "damage inflicted by arrogant customs officers, airport police, vengeful Paris bellhops and opium-fogged Pakistani cabbies were entirely cosmetic".[18]

In 1981, the daily Israeli newspaper Maariv, provided several Osborne 1 to its reporters. The computers were equipped with acoustic couplers. This configuration allowed a reporter to submit an article digitally directly from the field to the newsroom. Maariv used a localized version of Osborne 1 that supported Hebrew.[citation needed]

In popular culture[edit]

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


  1. ^ "Xerox NoteTaker". Computer History. Retrieved May 21, 2010.
  2. ^ a b c "Osborne 1". OldComputers.net. Retrieved May 21, 2010.
  3. ^ a b Fallows, James (July 1982). "Living With a Computer". Atlantic Magazine. Retrieved May 21, 2010.
  4. ^ "Computers: Carry Along, Punch In, Read Out". Time. Time Inc. June 21, 1982. Retrieved April 3, 2011.
  5. ^ McCracken, Harry (April 1, 2011). "Osborne!". Technologizer. Retrieved April 3, 2011.
  6. ^ Morgan, Chris (April 1981). "New Trends in Portability: The Osborne 1". BYTE. p. 8. Retrieved October 18, 2013.
  7. ^ a b Hogan, Thom (April 13, 1981). "Osborne Introduces Portable Computer". InfoWorld. IDG. p. 1. Retrieved April 4, 2011.
  8. ^ a b c Dahmke, Mark (June 1982). "The Osborne 1". BYTE. p. 348. Retrieved October 19, 2013.
  9. ^ Advertisement (September 1982). "The $1795 Business Computer that is changing the way people go to work". BYTE. p. 31. Retrieved October 19, 2013.
  10. ^ a b Grzanka, Leonard G. (January 1984). "Requiem for a Pioneer". Portable Computer.
  11. ^ Rothman, David H. (1985). The Silicon Jungle. New York: Ballantine Books. p. 33. ISBN 0-345-32063-8.
  12. ^ "The Portable Companion". Retrieved August 1, 2009.
  13. ^ Lee Felsenstein (February 12, 2009). "email to PBA Galleries".
  14. ^ a b c d e f g h Hogan, Thom (1982). Osborne 1 Technical Manual. Mike Iannamico (2F00153-01 ed.). Osborne Computer Corporation.
  15. ^ http://www.kev.pulo.com.au/osborne1/documents/o1screenpacusersguide.pdf Screen-Pac User Guide, retrieved 2017 Oct 03
  16. ^ "Draw Cards Using MBASIC". The Portable Companion. August–September 1982. ISSN 0732-7501.
  17. ^ Pournelle, Jerry (April 1982). "The Osborne 1, Zeke's New Friends, and Spelling Revisited". BYTE. p. 212. Retrieved October 19, 2013.
  18. ^ Kline, David (July 1982). "Osborne—Behind Guerrilla Lines". Microcomputing. pp. 42–50. Retrieved 15 February 2016.

Further reading[edit]

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