The H-89 was sold under the two names: Heathkit H-89 and Zenith Data Systems Z-89. The H-89 was sold in kit form, the Z-89 came assembled.
It originally came with 16 KB of memory, later versions provided up to 48KB on the main CPU board (in groups of 1 KB chips). Zenith and Heathkit offered a 16 KB expansion card ($120) for a total of 64 KB when using CP/M.
The system was identical to the H-19 video terminal but had an additional CPU board between the CRT and the terminal board. (Really identical because Heath offered upgrade kits to convert an H-19 to an H-88/H-89 computer).
It used hard sectored disks with a built-in card controller. Under either H-DOS or CP/M, disk capacity was of 90 KB. Another model the H-88 was identical to the H-89, but did not include the floppy drive or controller. It had a cassette port.
A couple of years later, the H/Z-37 soft sectored controller and ROMS came out, then was replaced with a double 5.25" floppy disk drive called H/Z-87 (102 KB, 250 ms). A double 8" floppy disk drive called H/Z-47 (1 Mb each) and a hard disk called H/Z-67, it contained one 10MB 8" winchester drive and one 8" floppy drive (like the one in the H/Z-47).
It ran under HDOS or CP/M (the operating system used 16 KB of RAM).
HDOS was originally written for the H-8, it ran without modification on the '89. This was a single-user OS written by J. Gordon Letwin for Heath. It included a Basic interpreter and assembler.
For CP/M, H/Z wrote a custom BIOS in assembler that the new user could further customize for his specific hardware and assemble right on the machine.
A version of MP/M was also available for the system.
A lot of extension boards were available for this computer including 64 KB memory boards, hard-disk controller cards, 3-port serial I/O board, H19 terminal board, etc.
A third party small upgrade card was also offered which doubled the processor speed to 4 Mhz.
An assembler/debugger was given with the DOS. A paper tape reader was available as well. Microsoft has adapted its various programming languages (Basic, Fortran, Cobol) for this computer. Borland also offered a version of Turbo Pascal that worked great with the CP/M.
Dennis reports:
The base H-89 had no graphic modes, just 33 graphic characters. At least two different add-on boards were created that gave the H-89 bitmapped graphics capabilities, but I'm pretty sure they both required hardware modifications to tie them in to the terminal board - this was not a simple plug-in expansion card
This was the first computer my father bought so he could research how to do fusion through computer programming. My brother designed a Pacman program on (it was very primitive in the graphics area), and I did writing. It had to be booted up with a disk, and in those days, software did not have backups. One time I was saving a file, and it was too big for the disk, for the computer abandoned it!
Wanted this computer. I will pay any postage costs!
megabyte2003(at)list.ru
Tuesday 20th March 2012
Sergey (Moscow, Russia)
I was given one of these by one of my lecturers when I finished at university in 1983. Great fun. I modified it to so you it could switch to run at 4.096MHz (double speed). It had no soft sectored controller and Heath had stopped making them so I made myself one on veroboard, but using a more modern (but compatible) controller chip to make it easier to build. Later I added a RAM disk by, among other things, replacing all the old 16Kb RAM chips with 8 more modern 256Kb chips. I stopped using it once I got an Amstrad PC2286 and later sold it for £50.
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