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COMPUTOPEDIA / PERSONAL COMPUTERS / ZENITH / Z-100

Zenith Z-100

Zenith Data Systems' Z-100 was a dual-CPU personal computer that ran both MS-DOS and CP/M-86, marketed alongside a nearly identical kit version called the H-100, with which it shared all major components except front-panel branding.

The Z-100 featured a dual-processor architecture: an Intel 8088 handling 16-bit operations and an 8085 managing 8-bit CP/M tasks2. This allowed users to switch control to the 8085 to run CP/M programs, which could access files stored under Z-DOS, bridging two operating environments in a single machine9. Despite being labeled an "18-Bit-Rechner" in at least one contemporary publication, the technical basis for this designation remains undocumented in surviving materials1. The system ran Zenith's implementations of MS-DOS versions 2 and 3, as well as CP/M-86 and the 8-bit variant CP/M-851245811.

Expansion options included a Real-Time Clock (CB-5063-30) priced at $59.0011 and the SmartWatch from FBE Research, a plug-in module with a ten-year battery that maintained time and date across reboots by installing in the ROM socket26. The machine supported a Monochrome/Color Video Card (Z-409) for $239.0011 and featured a light-pen port, with at least one third-party vendor, Software Wizardry of St. Charles, Missouri, offering a compatible light pen and associated graphics software9. Printer drivers were available for several models, including the Okidata Microline, Zenith/MPI 99/150, Anadex Silent Scribe, and IDS Paper Tiger457.

Storage configurations varied widely. A Winchester hard disk setup with a 20MB formatted drive was listed at $478.00 in one source2 and $448.00 in another, indicating either a price drop or conflicting reporting6. Complete systems with Seagate drives offered 21MB for $632.00 or 31MB for $727.00, excluding drive and controller610. A more modular option, the Complete Hard Disk System for internal mounting, included an S-100 bus board, XT controller, EasyWin software, and installation hardware for $288.00, requiring a separately ordered Seagate ST-125 or ST-138 drive14. Floppy disk capacities were modest: 155K for single-sided double-density (SSDD) and 304K for double-sided double-density (DSDD)15.

Memory expansion was handled via plug-in kits. MEMORY KIT #150-256-18 included a ZPAL chip and eighteen 256K 150 ns RAM chips, upgrading a base 128K system to 640K or a 256K system to 704K26. For motherboards with part number 181-4918 or higher, a PAL Chip Set ($64.00) enabled the use of 256K RAM chips and, when combined with a new video card, allowed total memory to reach 768K14. The CDR Z-100 SPEED MODULE enabled operation at 7.5 MHz, switchable externally between speed and normal modes, and required no soldering for installation61014. Optional 8087 math coprocessors were offered at 5 MHz ($129.00) and 8 MHz ($165.00)26.

Software pricing revealed aggressive discounting. Z-Basic (16-bit), list $175.00, sold for $24.00; Multiplan dropped from $195.00 to the same price point610. The Condor File Manager, originally $299.00, was available for $24.00, and a package containing four major software titles (PK-100-4) was discounted from $819.00 to $62.00610. Even Microsoft BASIC-80 (8-bit) and Peachtree Inventory Management saw steep cuts, from $175.00 to $24.00 and $499.00 to $38.00 respectively610.

Despite its technical sophistication, the Z-100 faced internal contradictions. Zenith's shift toward PC-compatibility led software partners like Hilgraeve to realign, and reports indicated that Zenith's own implementation of Windows "doesn't seem to be working correctly, in some respects"13. Yet the Z-100 PC variant became the company's most popular model, adopted by several major OEMs12. Ken Skier's hardware review in BYTE was "suitably glowing"9, and user sentiment ran high: "LOVE the Z-100 computer, and think the Zenith users are the best in the world" appeared in multiple issues of remark316.

The H-100 kit version shared all major components with the Z-100, differing only in 4 square inches of front-panel plastic housing the product logo9. Marketing materials often obscured this near-identity, suggesting a greater divergence than engineering reflected9. The H-100 Desktop Computer (HS-1108-41) was priced at $999.00, while the Advanced Personal Computer (HS-241) carried a $2,499.00 tag11.

References

  1. ComputerPersoenlich 83 08
  2. remark-volume8-issue1-1987 (1987)
  3. remark-volume5-issue3-1984 (1984)
  4. remark-volume10-issue1-1989 (1989)
  5. remark-volume9-issue1-1988 (1988)
  6. remark-volume8-issue7-1987 (1987)
  7. remark-volume11-issue1-1990 (1990)
  8. remark-volume7-issue3-1986 (1986)
  9. 1984 06 BYTE 09-06 Computers and Education (1984)
  10. remark-volume8-issue6-1987 (1987)
  11. remark-volume7-issue10-1986 (1986)
  12. remark-volume6-issue1-1985 (1985)
  13. remark-volume8-issue9-1987 (1987)
  14. remark-volume11-issue4-1990 (1990)
  15. 1985 05 Dr Dobbs Journal (1985)
  16. remark-volume5-issue2-1984 (1984)