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H > HEATHKIT / ZENITH  > Z-100/110/120   


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...

Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).


An awesome machine. The Desktop 4 contract with the US government really hurt HeathKit. We ended up selling these computers below cost. The H-100 (Z-100) was one of the best computer we made. Baboo Rajaram really knew what he was doing. To bad they canceled the 286 version. Had the wire-wrapped 286 test machine for years.

Friday 6th April 2012
Big al (St. Joseph Michigan)

My very first computer was an H100 with 256K RAM. I joke with students now that their watch has more current computing power. But for its day, it was a great machine. I wrote my PhD dissertation on it with Peachtext word processing software and a Toshiba dot matrix printer.

Tuesday 15th October 2019
John McLaughlin

Best keyboard for writing ever made ! still have mine with 8 inch drives !!!!

Tuesday 23rd September 2014
greg greene (Canada)


NAME  Z-100/110/120
MANUFACTURER  Heathkit / Zenith
TYPE  Professional Computer
YEAR  june 1982
KEYBOARD  Full-stroke keyboard with separated numeric keypad and function keys. 95 keys.
CPU  Intel 8085 (8 bits) @ 5 MHz & Intel 8088 (16 bits) @ 5 MHz
RAM  128 KB, up to 768 KB through 64 KB or 256 KB modules
VRAM  64 KB (up to 192 KB)
ROM  16 KB (boot + control tests), up to 64 KB
TEXT MODES  80 x 24 + 1 independant line. (characters matrix : 8 x 9)
GRAPHIC MODES  640 x 500 (semi-graphic mode with 33 special characters available), 640 x 225 (8 colors) - available with a color monitor
SOUND  Built-in speaker
SIZE / WEIGHT  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
I/O PORTS  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
BUILT IN MEDIA  2 x 5''1/4 disk-drives (320 KB each)
OS  CP/M 86, Z-DOS, MS-DOS, Forth-Multix, Prologue
POWER SUPPLY  Built-in Power Supply Unit
PRICE  About $1,800+ - 7408 (France, february 1983)

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