Zenith Z-89

The Z-89 was a personal computer produced by Zenith Data Systems (ZDS) in the early 1980s.

Heathkit computer H88.JPG
8-bit Heathkit H88 computer[1]
ManufacturerZenith Data Systems (ZDS)
TypePersonal computer
Release date1979; 42 years ago (1979)
Introductory priceKit version with 1 floppy drive: US$1800 in 1979 (circa equivalent to $6,300 in 2019)
Discontinued1985 (1985)
Operating systemHDOS, CP/M, UCSD Pascal (P-System Pascal), or MP/M
CPU2x 2.048 MHz Zilog Z80 (one for the terminal)
MemoryRAM: 16 KB – 48 KB on main board, optional 16 KB memory card (max addressable: CP/M - 64 KB, HDOS - 56 KB)
Connectivity3 serial, 1 Centronics parallel (optional), external diskette drive connector
Heathkit H89 aka Zenith Z-89. This unit has two half-height DD diskette drives in place of the single full-height original.
Zenith Z-89 in Paris 2008


It was based on the Zilog Z80 microprocessor running at 2.048 MHz, and supported the HDOS and CP/M operating systems. The 2295 USD Zenith Z-89 was integrated in a terminal-like enclosure with a non-detachable keyboard, 12-inch monochrome CRT with a 80x25 screen, 48 KB RAM, and a 5.25" disk drive.[2]

In 1979, prior to Zenith's purchase of Heath Company, Heathkit had originally designed and marketed this computer in kit form as the Heath H89, assembled as the WH89, and without the floppy but with a cassette interface card as the H88. (Note: Prior to the Zenith purchase, the Heathkit model numbers did not include the - 'dash').

Heath/Zenith also made a serial terminal, the H19/Z-19, based on the same enclosure (with a blank cover over the diskette drive cut-out) and terminal controller. They even offered an upgrade kit to convert the terminal into a full H89/Z-89 computer.

Another configuration, the Z-90, changed the floppy drive controller from the hard-sectored controller (max 100 kB) to a soft-sectored controller that supported double-sided, double density, 96 tpi drives with a capacity of 800 kB. It also came standard with 64 KB of RAM.

There were several external drive systems available for the H89/Z-89.

  • The H77/Z-77 and H87/Z-87 supported up to two additional Single-Sided, Single Density, 48 tpi 5.25" drives. When connected to the standard hard-sectored controller, it could store 100 kB each. By connecting it to a soft-sectored controller, they could store 200 kB.
  • The H37/Z-37 supported up to two Double-Sided, Double Density, 96 tpi 5.25" drives and required the soft-sectored controller. These drives had a capacity of 800 kB each.
  • The Z-47 supported two 8" floppy drives and required its own controller. These used the standard IBM 3740 floppy disks and had a capacity of 1.2 MB each.
  • The Z-67 was a 10 MB Winchester Drive plus one 8" floppy drive and also required its own controller.
  • In France, the Heath/Zenith Data System branch connected the 10 MB removable cartridge hard disk, manufactured by Bull in Belfort

A maximum of two disk controller cards could be installed in a standard system.


BYTE wrote that the H-89 "has a number of unique hardware features and the same excellent software support and documentation as the original H-8 system".[2]


Display integral 12" monochrome CRT (choice of white, amber, or green), 80 × 25 characters (25th line was a special status line)
Storage 5.25" diskette drive (originally hard-sectored, 100 KB)
Operating System HDOS, CP/M, UCSD Pascal (P-System Pascal), or MP/M


  1. ^ Collection www.yesterpc.org
  2. ^ a b Dahmke, Mark (August 1980). "The Heath H-89 Computer". BYTE. p. 46. Retrieved 18 October 2013.
  1. ^ Inflation Conversion Factors for Dollars

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