IMSAI 8080

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IMSAI 8080
IMSAI 8080-IMG 1477.jpg
Manufacturer IMS Associates, Inc., later
IMSAI Manufacturing Corporation
Type Hobbyist computer,
aluminum casing,
22-slot motherboard, S-100 bus
Release date December 1975; 41 years ago (1975-12)[1]
Discontinued 1978 (1978)
Operating system First commercial supplier of
Digital Research's CP/M, later followed by derived IMDOS
CPU Intel 8080/8085A @ 2 MHz/3 MHz
Memory 256/4K bytes on a 4K board (static), 16K, 32K, 64K DRAM
Storage Optional cassette or 514" and 8" floppy drives,
hard drives (CDC Hawk
5 MB fixed, 5 MB removable)[2]
Closeup of IMSAI 8080 front panel
1977-1979 desktop computer, Intel 8085, 32KB/64 kb RAM, 2x fdd 80/160 kb, S100 Bus. 2kb monitor ROM, 2kb Video ROM

The IMSAI 8080 was an early microcomputer released in late 1975, based on the Intel 8080 and later 8085 and S-100 bus.[1] It was a clone of its main competitor, the earlier MITS Altair 8800. The IMSAI is largely regarded as the first "clone" microcomputer. The IMSAI machine ran a highly modified version of the CP/M operating system called IMDOS. It was developed, manufactured and sold by IMS Associates, Inc. (later renamed IMSAI Manufacturing Corp). In total, between 17,000 and 20,000 units were produced from 1975 to 1978.


In May 1972, William Millard started businesses individually as IMS Associates (IMS) in the areas of computer consulting and engineering, using his home as an office. By 1973, Millard founded IMS Associates, Inc. Millard soon found capital for his business, and received several contracts, all for software.

In 1974, IMS was contacted by a client which wanted a "workstation system" that could complete jobs for any General Motors new-car dealership. IMS planned a system including a terminal, small computer, printer, and special software. Five of these work stations were to have common access to a hard disk drive, which would be controlled by a small computer. Eventually product development was stopped.

Millard and his chief engineer Joe Killian turned to the microprocessor. Intel had announced the 8080 chip, and compared to the 4004 to which IMS Associates had been first introduced, the 8080 looked like a "real computer". Full scale development of the IMSAI 8080 was put into action (using the existing Altair 8800's S-100 bus), and by October 1975 an ad was placed in Popular Electronics, receiving positive reactions.[3]

IMS shipped the first IMSAI 8080 kits on 16 December 1975, before turning to fully assembled units.[4] In 1976, IMS was renamed to IMSAI Manufacturing Corporation because by then, they were a manufacturing company, not a consulting firm.

In 1977, IMSAI marketing director Seymour I. Rubinstein paid Gary Kildall $25,000 for the right to run CP/M version 1.3, which eventually evolved into an operating system called IMDOS, on IMSAI 8080 computers.[5][6][7][8] Other manufacturers followed and CP/M eventually became the de facto standard 8-bit operating system.

By October 1979, the IMSAI corporation was bankrupt. The 'IMSAI' trademark was acquired by Thomas "Todd" Fischer and Nancy Freitas (former early employees of IMS Associates), who continued manufacturing the computers under the IMSAI name as a division of Fischer-Freitas Co. Support for early IMSAI systems continues to this day.[9]

IMSAI 8080
Floppy disk unit

IMSAI Series Two[edit]

The IMSAI Series Two is a personal computer which combines modern hardware with the original IMSAI 8080 hardware and case, with the original front panel LEDs and switches. The Series Two supports USB and Ethernet and is a co-operative development from Howard Harte (Harte Technologies LLC.) and Thomas Fischer (Fischer-Freitas Company). It has no relation to the original IMS Associates, Inc. (later known as IMSAI Manufacturing Corporation).

Several options are available for the IMSAI Series Two, such as a Mini Drive enclosure for external drives.

VDP series[edit]

In 1978/79 IMSAI released the VDP-series, based on the 8085. According to the product description of January 1979, quite some different models were released 32 and 64 K memory, 9" (VDP4x-range) and 12" (VDP8x-range) video display. For example, the VDP-40 had 2 5 1/4" disk drives, a 9" 40 character wide display and a 2 K ROM Monitor all in one cabinet. The built-in keyboard had a 8035 microprocessor and a serial interface to the main board. The VIO-C video board had 2k firmware ROM, 2k character generator ROM with 256 characters and 2 K refresh memory.

The VDP80/1050 was listed in Januari 1979 for $10920 and the VDP-40/64 for $7466.

IMSAI in popular culture[edit]

An IMSAI 8080 and an acoustic coupler type modem were among the hacking tools used by the main character in the 1983 movie WarGames [1].

An IMSAI 8080 can also be spotted being used as a prop in an office scene approximately 13 minutes into Sidney Lumet's 2007 crime-drama-thriller film Before the Devil Knows You're Dead.

See also[edit]

Further reading[edit]


  1. ^ a b THE HISTORY OF IMSAI- The Path to Excellence, IMSAI of Fischer-Freitas Company (original text 1978)
  2. ^ Press Release: IMSAI Announces Hard Disk
  3. ^ IMS Associates, Inc. (October 1975). "IMASI and Altair Owners". Popular Electronics. Ziff Davis. 8 (4): 110.  Advertisement: IMSAI 8080 computer with 1K of RAM. $439 kit, $621 assembled.
  4. ^ Littman, Jonathan (1987). Once Upon a Time in ComputerLand: The Amazing, Billion-Dollar Tale of Bill Millard. Los Angeles: Price Stern Sloan. p. 18. ISBN 0-89586-502-5.  "Later that day, December 16 [1975], United Parcel Service picked up the first shipment of 50 IMS computer kits for delivery to customers."
  5. ^ Wallace, James; Erickson, Jim (1993). Hard Drive: Bill Gates and the Making of the Microsoft Empire. New York: HarperBusiness. ISBN 0-88730-629-2. 
  6. ^ Kildall, Gary Arlen (January 1980). "The History of CP/M, The Evolution of an Industry: One Person's Viewpoint" (Vol. 5, No. 1, Number 41 ed.). Dr. Dobb's Journal of Computer Calisthenics & Orthodontia. pp. 6–7. Retrieved 2013-06-03. […] The first commercial licensing of CP/M took place in 1975 with contracts between Digital Systems and Omron of America for use in their intelligent terminal, and with Lawrence Livermore Laboratories where CP/M was used to monitor programs in the Octopus network. Little attention was paid to CP/M for about a year. In my spare time, I worked to improve overall facilities […] By this time, CP/M had been adapted for four different controllers. […] In 1976, Glenn Ewing approached me with a problem: Imsai, Incorporated, for whom Glenn consulted, had shipped a large number of disk subsystems with a promise that an operating system would follow. I was somewhat reluctant to adapt CP/M to yet another controller, and thus the notion of a separated Basic I/O System (BIOS) evolved. In principle, the hardware dependent portions of CP/M were concentrated in the BIOS, thus allowing Glenn, or anyone else, to adapt CP/M to the Imsai equipment. Imsai was subsequently licensed to distribute CP/M version 1.3, which eventually evolved into an operating system called IMDOS. […] 
  7. ^ Shustek, Len (2016-08-02). "In His Own Words: Gary Kildall". Remarkable People. Computer History Museum. 
  8. ^ Kildall, Gary Arlen (2016-08-02) [1993]. Kildall, Scott; Kildall, Kristin, eds. "Computer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry" (Manuscript, part 1). Kildall Family. Retrieved 2016-11-17. 
  9. ^ "Company: IMS Associates, Inc. (IMSAI)". Retrieved 2008-10-27. 

External links[edit]