1980s Vintage Computers

Zenith Z-100

Zenith Z120

The Zenith Z-100 (also sold as the Heath Z-100 by Heathkit) was an innovative design which combined an 8-bit Z80 processor (to run CP/M) with a 16-bit 8088 processor (to run Zenith's version of MS-DOS, know as ZDOS). It has a large motherboard and can be expanded due to having four S-100 slots. There were two models, mine (the Z-120, now sold) features:

  • A single box design with built in screen, keyboard and disk drives.
  • Built in green screen, with a mix of 80 column text or 640x200 graphics (colour output on CGA socket).
  • Z-80 processor running at 4 MHz.
  • 8088 processor running at 5Mhz.
  • 192K of user RAM , plus 48K of video RAM.
  • Built in serial and parallel ports.
  • Twin 360 KB floppy drives (uses soft-sector floppies), in double density double sided mode.
  • Basic diagnostics on ROM.

Zenith also made a model without a display called the Z-110.

This computer was introduced in around 1982. It was quite popular in the US, but in the UK it was not very popular.


There is an excellent archive of Z-100 documents and software at: http://planemo.org/retro/definitive-z-100-software-manual-repository/

There was a site with Z-100 boot disks at: http://www.computernostalgie.site90.net/ZenithZ100 but this site appears not to be maintained, it was copied to the Internet Archive. The disk images don't appear to be copied, I had downloaded some of them and have uploaded these to Dropbox.

Zenith Z-100 pages can be found at:



This page was last revised on: 16/11/14