Zenith Z-100

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

Zenith Z-100
ManufacturerZenith Data Systems
Typepersonal computer
Release dateJune 1982 (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]

Design

The Zenith Data Systems Z-100 is a pre-assembled version of the Heathkit H100 electronic kit.[2] 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.[3] Both models have a built-in keyboard that was modeled after the IBM Selectric typewriter.[3]

  • Dual processors: 8085 and 8088.
  • Available with CP/M and Z-DOS (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.
  • 2× serial ports (2661 UART), one Centronics printer port (discrete TTL chips), light pen port.
  • 640×225 bitmap display. 8 colors (low-profile model), or monochrome upgradable to 8 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).

The Z-100 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 use IBM BIOS extensions and do not run,[4] including Lotus 1-2-3.[5] 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,[4] superior to the contemporary CGA (640×200 monochrome bitmap or 320×200 4-color), IBM Monochrome Display Adapter (MDA) (80×25 monochrome text-only), and with 8 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.[6]

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

Uses

In 1983, Clarkson College of Technology (now Clarkson University) became the first college in the nation to give each incoming freshman a personal computer. The model issued to them was the Z-100.[7][8][9]

Reception

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".[4][5] Although forced to buy a real IBM PC because of the Z-100 and other computers' incomplete PC compatibility,[5] he reported in December 1983 that a friend who was inexperienced with electronic kits was able to assemble a H100 in a day, with only the disk controller needing soldering.[2]

References
  1. Zenith challenges IBM's share of micro market, By Paul Freiberger, Page 35, InfoWorld, 13 September 1982
  2. Pournelle, Jerry (December 1983). "Buddy, Can You Spare a Door Latch?". BYTE. p. 59. Retrieved 20 October 2013.
  3. http://www.computinghistory.org.uk/det/44090/Zenith-Z-100/
  4. Pournelle, Jerry (June 1983). "Zenith Z-100, Epson QX-10, Software Licensing, and the Software Piracy Problem". BYTE. p. 411. Retrieved 20 October 2013.
  5. Pournelle, Jerry (September 1983). "Eagles, Text Editors, New Compilers, and Much More". BYTE. p. 307. Retrieved 2019-04-07.
  6. One Company's CAD Success Story, InfoWorld, 3 December 1984, retrieved 19 July 2014
  7. "Computers to Come With Books at Drexel U." New York Times. October 28, 1982. Retrieved 9 December 2013.
  8. "Supershorts". Computer World. August 15, 1983. Retrieved 9 November 2011.
  9. "Clarkson College to Issue Computers to Student Body" (PDF). Silicon Gulch Gazette. February 1983. Retrieved 9 November 2011.
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