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Zenith Z-100

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Zenith Z-100
ManufacturerZenith Data Systems
Typepersonal computer
ReleasedJune 1982; 43 years ago (1982-06)
Operating systemAvailable with CP/M-80, CP/M-86 and Z-DOS (non-IBM compatible MS-DOS variant)[1]
CPUDual processors: 8085 and 8088[1]
MemoryBase 128 KB RAM, expandable to 192 KB on board, to 768 KB with S-100 cards. (Video RAM was paged into the 64 KB block above 768 KB).
StorageTwo 320 KB 40-track double-sided 5.25-inch Floppy disk drives. Socket enabled direct plug-in of external 8-inch floppies.
Display25 lines × 80 characters[1]
Graphics640×225 bitmap display. 8-color (low-profile model), or monochrome upgradable to 8-level greyscale (all-in-one).[1]
Input2× serial ports (2661 UART), one Centronics printer port (discrete TTL chips), light pen port
Power300 watts[1]

The Z-100 computer is a personal computer made by Zenith Data Systems (ZDS). It was a competitor to the IBM PC.

Design

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The Zenith Data Systems Z-100 is a pre-assembled version of the Heathkit H100 electronic kit,[2] but unlike the Zenith Z-89 that Heathkit created, the Z-100 was designed first as a preassembled product.[3] Design began in March 1981 for a Z-89 successor with faster processor, improved graphics, support for memory beyond 64K, and more sophisticated operating systems.[4]

In the same family, the Z-120 is an all-in-one model with self-contained monitor, and the Z-110 (called the low profile model) is similar in size to the cabinet of an IBM PC.Both models have a built-in keyboard that was modeled after the IBM Selectric typewriter.[5]

  • Dual processors: 8085 and 8088.
  • Available with CP/M and Z-DOS[1] (non-IBM compatible MS-DOS variant).
  • Five S-100 expansion slots.
  • Two 320 KB 40-track double-sided 5.25-inch floppy disk drives. Socket enabled direct plug-in of external 8-inch floppies.
  • Two serial ports (2661 UART), one Centronics printer port (discrete TTL chips), light pen port.
  • 640×225 bitmap display, with eight colors (low-profile model), or monochrome upgradable to eight greyscales (all-in-one).
  • Base 128 KB RAM, expandable to 192 KB on board, to 768 KB with S-100 cards. (Video RAM was paged into the 64 KB block above 768 KB).

Zenith stated that the Z-100 would be compatible with most Intel 8080 and Z-89 software.[3][4] The computer is partially compatible with the IBM PC, using standard floppy drives. It runs a non-IBM version of MS-DOS, so generic MS-DOS programs run, but most commercial PC software uses IBM BIOS extensions and do not run,[6] including Lotus 1-2-3.[7] Several companies offered software or hardware solutions to permit unmodified PC programs to work on the Z-100.

The Z-100 has unusually good graphics for its era,[6] superior to the contemporary CGA (640×200 monochrome bitmap or 320×200 four-color), IBM Monochrome Display Adapter (MDA) (80×25 monochrome text-only), and with eight colors or grayscales available at a lower resolution than the Hercules Graphics Card (720×348 monochrome). Early versions of AutoCAD were released for the Z-100 because of these advanced graphics.[8]

Aftermarket vendors also released modifications to upgrade mainboard memory and permit installation of an Intel 8087 math coprocessor.

Uses

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In 1983, Clarkson College of Technology became the first college in the nation to give each incoming freshman a personal computer. The model issued to them was the Z-100.[9][10][11] Each student paid $1800 for the computer during their time at Clarkson.[12]

Reception

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Jerry Pournelle in 1983 praised the Z-100's keyboard, and wrote that it "had the best color graphics I've seen on a small machine".[6][7] Although forced to buy a real IBM PC because of the Z-100 and other computers' incomplete PC compatibility,[7] he reported in December 1983 that a friend who was inexperienced with electronic kits was able to assemble a Z-100 in a day, with only the disk controller needing soldering.[2] Ken Skier praised the computer's reliability in the magazine in January 1984 after using the computer for more than 40 hours a week for eight months. While criticizing its inability to read other disk formats, he approved of Zenith's technical support, documentation, and keyboard and graphics. Skier concluded that those who "want a well-designed, well-built, well-documented system that runs the best of 8-bit and 16-bit worlds" should "consider the Zenith Z-100".[13] "Simply put", InfoWorld wrote, "this is an excellent machine". Graphics, keyboard, adherence to industry standards, 90-day on-site service ("something you'd expect if you dropped $1 million on a mainframe"), and bundled software were among the features the magazine approved of. While wishing for tutorial documentation, detachable keyboard, and quieter fan, InfoWorld concluded "This is a superb machine".[14]

References

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  1. ^ a b c d e f Freiberger, Paul (1982-09-13). "Zenith challenges IBM's share of micro market". InfoWorld. p. 35. Retrieved 2025-03-19.
  2. ^ a b Pournelle, Jerry (December 1983). "Buddy, Can You Spare a Door Latch?". BYTE. p. 59. Retrieved 10 September 2024.
  3. ^ a b Mace, Scott (1982-04-12). "Zenith working on 16-bit micros". InfoWorld. pp. 1, 4. Retrieved 2025-03-16.
  4. ^ a b Zimmerman, Frederick (Winter 1983). "HUGCon 1". Sextant. No. 4. pp. 7–34. Retrieved January 24, 2026.
  5. ^ "Zenith Z-100 - Computer - Computing History".
  6. ^ a b c Pournelle, Jerry (June 1983). "Zenith Z-100, Epson QX-10, Software Licensing, and the Software Piracy Problem". BYTE. p. 411. Retrieved 10 September 2024.
  7. ^ a b c Pournelle, Jerry (September 1983). "Eagles, Text Editors, New Compilers, and Much More". BYTE. p. 307. Retrieved 2019-04-07.
  8. ^ One Company's CAD Success Story, InfoWorld, 3 December 1984, retrieved 19 July 2014
  9. ^ "Computers to Come With Books at Drexel U." New York Times. October 28, 1982. Retrieved 9 December 2013.
  10. ^ "Supershorts". Computer World. August 15, 1983. Retrieved 9 November 2011.
  11. ^ "Clarkson College to Issue Computers to Student Body" (PDF). Silicon Gulch Gazette. February 1983. Retrieved 9 November 2011.
  12. ^ Zimmerman, Frederick (March–April 1984). "A Z100 on Every Desk: Clarkson College". Sextant. No. 9. pp. 8–14. Retrieved February 12, 2026.{{cite magazine}}: CS1 maint: date format (link)
  13. ^ Skier, Ken (January 1984). "The Zenith Z-100". BYTE. pp. 268–278. Retrieved 2021-11-06.
  14. ^ Robinson, Phillip (1983-11-07). "Review: Zenith Z-100". InfoWorld. Vol. 5, no. 45. pp. 91, 94–95. Retrieved January 24, 2026.
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