Zenith Z-89
| Company type | Company |
|---|---|
| Industry | Computer hardware |
| Founded | 1979 |
| Headquarters | United States |
| Products | Z-89 personal computer |
The Z-89 is a personal computer launched in 1979 by Heathkit and primarily manufactured by Zenith Data Systems during the early 1980s. This model combines an enhanced version of the Heathkit H8 microcomputer with the H19 terminal, housed within a redesigned case that incorporates a built-in floppy disk drive adjacent to the screen. Equipped with a Zilog Z80 processor, it supports both CP/M and Heathkit’s own HDOS operating systems.
Description
The Zenith Z-89 is powered by a 2.048 MHz Zilog Z80 CPU and offers compatibility with both HDOS and CP/M. Retailing for US$2295, it features a terminal-style chassis with an integrated keyboard, a 12-inch monochrome CRT capable of displaying 80 columns by 25 rows, 48 KB of RAM, and an internal 5.25" floppy disk drive.
Its premium keyboard includes numerous special-function keys such as REPEAT, ESC, TAB, CAPS, CTRL, SCROLL, RESET, BREAK, BACK SPACE, LINE FEED, DELETE, along with five function keys and a numeric keypad. The display supports reverse video mode and character-based graphics.
Inside the enclosure are two card cages, each accommodating up to three expansion cards compatible with the Benton Harbor Bus. Upgrade options included disk controller cards; a 16 KB RAM expansion card increasing total memory to 64 KB; a RAM drive card designed to bypass the Z80’s memory restrictions through specialized drivers; and multi-serial cards providing additional RS-232 ports. The CPU frequency could be boosted to 4 MHz.
Prior to Zenith’s acquisition of Heathkit in 1979, Heath marketed this system as the Heath H89 kit and the cassette-based H88. The company also offered the H19/Z-19 serial terminal which shared the same case design but lacked an integrated floppy drive; this terminal could be upgraded into a full H89/Z-89 computer via an available conversion kit.
The Z-90 model featured an improved floppy disk controller that replaced the hard-sectored controller (limited to 100 kB) with a soft-sectored unit supporting double-sided, double-density drives capable of storing up to 640 kB. It came standard with 64 KB of RAM.
Multiple external disk drive configurations were available:
- H77/Z-77 and H87/Z-87: offered up to two single-sided, single-density (48 tpi) 5.25" drives with soft-sectored controllers; each drive held up to 160 kB.
- H37/Z-37: supported up to two double-sided, double-density (96 tpi) 5.25" drives requiring soft-sectored controllers; each had a capacity of 640 kB.
- Z-47: provided support for two IBM-standard 8" floppy drives (1.2 MB each) through a dedicated interface card.
- Z-67: combined a Winchester hard disk (10 MB) with an 8" floppy drive on its own interface card.
- In France, Heath/Zenith collaborated with Bull's local branch to connect removable cartridge hard disks (10 MB) manufactured by Bull.
Systems could accommodate up to two disk controller cards simultaneously.
Reception
Creative Computing described the Heath H89 as "the most professional looking" microcomputer on the market and regarded it as "one of the finest" options under $3000, predicting it would make a significant impact if robust software support was established. BYTE praised the H89’s distinctive hardware design along with its superior software and documentation quality, recommending the addition of a second floppy drive for optimal HDOS performance.
Although some terminal-related issues arose when running Supercalc, Jerry Pournelle in 1982 considered the Zenith Z-19 "an excellent terminal" and among the top choices available.
Zenith acknowledged that marketing kit computers not sold fully assembled posed difficulties. As a result, their next model after the Z-89—the Zenith Z-100—was developed as a completely assembled system.
Summary
| Display | 12-inch monochrome CRT screen (available in white or green), featuring 80 columns by 25 rows of characters, including a dedicated status line |
| Storage | 5.25-inch floppy disk drive (initially hard-sectored) with a capacity of 100 KB |
| Operating System | HDOS, CP/M, UCSD Pascal (P-System Pascal), or MP/M |