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Zenith Z-100

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Title: Zenith Z-100  
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Subject: CP/M-86, List of machines running CP/M, Heathkit, Z100, Zenith Data Systems, HyperACCESS, Telengard, Timeline of DOS operating systems
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Zenith Z-100

The Z-100 computer is an early personal computer made by Zenith Data Systems (ZDS). It was an alternative to the hardware system that won the marketing shares war in the early to mid-1980s, the IBM PC/XT/AT succession or family of computers.


The Zenith Data Systems Z-100 was a pre-assembled version of the Heathkit H100 electronic kit.[1] Configured as a family (Z-120 was an all in one model, with self-contained monitor), the Z-110 (called the low profile model) was similar in size to the cabinet of an IBM PC, XT, or AT, but a bit shorter, and configured with a raised cabinet molding on the top surface within which one placed one's display monitor, designed to keep it from sliding off to either side or back. Both models had a built in keyboard that was tactilely and in appearance modeled on an IBM Selectric typewriter, the premier office machine of the day.

  • 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.
  • 2x serial ports (2661 UART), one Centronics printer port (discrete TTL chips), light pen port
  • 640x225 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 was a "near-compatible" system to the IBM PC, using standard floppy drives. It ran a non-IBM version of MS-DOS, so "generic MS-DOS" programs would run; but most commercial PC software used IBM BIOS extensions and would fail.[2] Several companies offered software or hardware solutions to permit unmodified PC programs to work on the Z-100.

The Z-100 had superior graphics to the contemporary CGA (640x200 monochrome bitmap or 320x200 4-color), IBM Monochrome Display Adapter (80x25 text-only), and arguably even the Hercules Graphics Card (720x348 monochrome). Early versions of AutoCAD were released for the Z-100 because of these advanced graphics.

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


In 1983, Clarkson College of Technology (now Clarkson University) required all incoming freshmen to purchase a Z-100 computer as part of their entry requirement, making it one of the first institutions to mandate computers for its students. [3][4]


Jerry Pournelle in June 1983 praised the Z-100's keyboard, and wrote that it "had the best color graphics I've seen on a small machine".[2] 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.[1]


External links

  • DigiBarn Computer Museum
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