---
title: HEATHKIT / ZENITH Z-100/110/120
categories:
- Computers
types:
- Professional Computer
origins:
- U.S.A.
years:
- '1982'
cpus:
- Intel 8085
params:
  name: Z-100/110/120
  image: /media/museum/photos/zenith_z100_system_s3.jpg
  company: /companies/heathkit-zenith
  company_name: HEATHKIT / ZENITH
  specs:
  - label: NAME
    value: Z-100/110/120
  - label: MANUFACTURER
    value: Heathkit / Zenith
  - label: TYPE
    value: Professional Computer
  - label: ORIGIN
    value: U.S.A.
  - label: YEAR
    value: june 1982
  - label: BUILT IN LANGUAGE
    value: Unknown
  - label: KEYBOARD
    value: Full-stroke keyboard with separated numeric keypad and function keys. 95 keys.
  - label: CPU
    value: Intel 8085 (8 bits) @ 5 MHz & Intel 8088 (16 bits) @ 5 MHz
  - label: RAM
    value: 128 KB, up to 768 KB through 64 KB or 256 KB modules
  - label: VRAM
    value: 64 KB (up to 192 KB)
  - label: ROM
    value: 16 KB (boot + control tests), up to 64 KB
  - label: TEXT MODES
    value: '80 x 24 + 1 independant line. (characters matrix : 8 x 9)'
  - label: GRAPHIC MODES
    value: 640 x 500 (semi-graphic mode with 33 special characters available), 640 x 225 (8 colors) - available with a color monitor
  - label: COLORS
    value: '8'
  - label: SOUND
    value: Built-in speaker
  - label: SIZE / WEIGHT
    value: |-
      Z-120 : 49,5 x 49,5 x 34,3 cm / 22,7 Kg\
      Z-110 : 49,5 x 49,5 x 18,1 / 18,1 Kg
  - label: I/O PORTS
    value: 2 x RS232 connectors, 1 x parallel / Centronics connectors, S-100 bus connector (IEEE 696), phone/light-pen connector, 5 x expansion slots, RGB connector, Composite video output
  - label: BUILT IN MEDIA
    value: 2 x 5''1/4 disk-drives (320 KB each)
  - label: OS
    value: CP/M 86, Z-DOS, MS-DOS, Forth-Multix, Prologue
  - label: POWER SUPPLY
    value: Built-in Power Supply Unit
  - label: PRICE
    value: About $1,800+ - 7408 (France, february 1983)
  tabs:
  - photos
  - adverts
  - links
  forum_thread: 271
  photos:
  - title: Z-110
    subtitle: ''
    text: ''
    image: /media/museum/photos/zenith_z100_system_s5.jpg
  - title: Z-120
    subtitle: ''
    text: ''
    image: /media/museum/photos/zenith_z100_1.jpg
  - title: Z-110 WITH MONITOR
    subtitle: ''
    text: Z-110 with Zenith monochrome green monitor.
    image: /media/museum/photos/zenith_z100_withmonitor_s1.jpg
  - title: SIDE VIEW
    subtitle: ''
    text: ''
    image: /media/museum/photos/zenith_z100_withmonitor_s2.jpg
  - title: RUNNING
    subtitle: ''
    text: Z-110 running a ZBASIC graphic demo.
    image: /media/museum/photos/zenith_z100_running_s1.jpg
  - title: OPENED
    subtitle: ''
    text: |-
      **(1)** Switching power supply unit\
      **(2)** S-100 slots\
      **(3)** Floppy disk controller. The flat cable provides connection to an external 8" or 5.25" FDD unit\
      **(4)** Dual full height 5.25" double sided, single density FDD's
    image: /media/museum/photos/zenith_z100_opened_s1.jpg
  - title: 'OPENED #2'
    subtitle: ''
    text: Keyboard and floppy disk drives are taken apart. Note the add-on video card fixed to the motherboard.
    image: /media/museum/photos/zenith_z100_inside_s1.jpg
  - title: MOTHERBOARD
    subtitle: ''
    text: |-
      **(1)** S-100 bus connectors. One of them is used for the FDD controller card\
      **(2)** Intel 8085 processor\
      **(3)** NEC V20 processor, 8 MHz compatible version of the 8088\
      **(4)** 16 KB BIOS ROM. Holds both CP/M et MS-DOS BIOS's\
      **(5)** Keyboard connectors\
      **(6)** 768 KB RAM chips - 3 banks of 8 x 41256 + 1 parity chip\
      **(7)** Video card connectors.
    image: /media/museum/photos/zenith_z100_motherboard_s1.jpg
  - title: USER'S MANUAL
    subtitle: ''
    text: ''
    image: /media/museum/photos/zenith_z100_manual_s1.jpg
  adverts:
  - title: FRENCH ADVERT (SEPTEMBER 1984)
    subtitle: ''
    text: ''
    image: /media/museum/pubs/zenith_z100_pub_1.jpg
  links:
  - title: Z-100 Life Line
    url: http://home.earthlink.net/~z100lifeline/
    text: Great resource for Z-100 serie computers
  oc_id: 261
  source:
    url: https://web.archive.org/web/20230417024943/http://www.old-computers.com/museum/computer.asp?c=261
    date: '2023-04-17'
---

The Z-100 series professional systems were bi-processor computers. They used an 8-bit Intel 8085 to keep the CP/M compatibility and thus run a wide range of professional software, and a 16-bit Intel 8088 to run MS-DOS or IBM PC/DOS OS's

Two models were released: the **Z-110** (pictured) which could display color graphics and was delivered with monochrome or colour monitor, and the **Z-120** which had a built-in monochrome (green, amber or white) monitor.

Z-Basic was the only language supported by Zenith directly. It was an extra-cost option on most packages. It could handle colors and graphics.

The professional keyboard was quite complete with 95 keys, a separate numeric keypad, 7 editing keys and 12 function keys. All the keys could be redefined by software.

A wide range of expansions could be added to the Z-100. They came from Zenith directly, or from third companies, installed by dealers: one or two 1 MB 8" disk drives, 5, 10 or 20 MB hard disk, 64 and 256 KB memory modules, expansion card with 6 x RS232 connectors, analogue/digital conversion card, etc. The computer also had five S-100 bus connectors which offered a lot of possibilities.

The Z-100 was a very fast machine, one of the fastest in its category in fact. It was thus often used in a multi-user configurations, using Forth-Multix or Prologue operating systems.

The 8088 ran at 5 MHz initially, and then later at 8 MHz. The first boards could handle 192K RAM, but later boards could have up to (and use) 768K on the main board. The default Video RAM was 64K, but allowed 3 banks for up to 192K for full color.

The disk controller had support for four 5.25" and four 8" floppy drives, though OSs including CP/M and Z-DOS supported only two of each. The earliest models (pictured here) had full height, but later models had half height drives. There was a hack later on that allowed for four 5.25" drives under MS-DOS 2.x. A Winchester hard disk (5 or 10 MB) could also be connected.

These models were also available as the **Heathkit H-100 series**, sold then as kits. In these versions the monitor and video boards were preassembled, but user actually had to assemble the controller board and the analog video circuit on the monitor board.

Here are some software available for the Z-100 serie: CP/M 85, CP/M 86, MS-DOS 2.0, Prologue, Forth-Multix, Assembler, interpreted & compiled Basic, Pascal, Fortran, Cobol, C language, Forth, Condor file manager, DBase II, Multilog, JTBase, Infostar, Lotus 1-2-3, Multiplan, Supercalc, Wordstar, Spellbinder...