Heath H8 computer, 2013

This Web page last updated date Mar 14 2013.


This Web page is about a H-8 Heath computer I acquired in 2005. It's an H-8 system and H-19 terminal. The owner originally purchased it in the late 1970's with upgrades in the early 1980's. I also have manuals and software for it, all from Heathkit.

In 2009 I did some testing work on it, and cataloged what it came with. Look at this linked Web page for details. In 2013 I ran it again under HDOS, to demonstrate at a computer festival.

For other support sites for Heath/Zenith 8-bit computers, check my H8 Web page. For other Heath Zenith computers, check my Heath/Zenith Web page for general descriptions, and for current information about the Heath company. If you have an early Heath and a Web site, I'll consider adding a link to your site. For other vintage computer restrorations I've done, check my repair restore Web pages.

H8 systems

[Heath H8 system] [H17 floppy drives] The H8 is an interesting machine in many respects. Offered in 1978, it has an OCTAL display and keyboard, not a binary front panel like other 8080 machines. The motherboard is SIDE mounted, not on the bottom, and uses a pin and socket connector and not an edge connector. (The H89 used similar connectors for their I/O cards.) Cards are supported on the far end from the bus with a bracket and brace system. Here's a view of the brace on the end of the card, also a convenient heat sink.

A shorter-length bus than the S-100 means it can run a little faster. Soem people have souped up their H8's to several Megahertz. And, there are Z80 and other upgrade cards which were built for this system. But the original used a cassette board for audio cassette tape file storage, like the early H89.

What did it cost?

$299 kit, H8 (case, front panel, CPU)
$575 kit, H17 floppy disk sysetm (floppy controler, drives in powered case)
$345 second H17 floppy disk drive
$ 95 H8-1 4K memory card
$175 kit, H8-4 four serial port card
$ 95 kit, H8-5 serial & cassette card
$ 99 kit, Trionyx Electronics, 64K memory board NO MEMORY CHIPS
$150 CP/M operating system
$150 HDOS operating system
$695 kit, H19 terminal
$??? H10 paper tape reader/punch (not part of Boston H8 system)

What did money buy in 1978?
gasoline was maybe 60 to 70 cents a gallon
Average US income - $17K
1978 Datsun 280Z - $5900 retail
median US home price - $55.7K

So the H8 system with floppy drives cost over $1500 in hardware in the late 1970's. That would have paid 1/4 the price of a new car; or cost around 10% of an annual average annual income.

2013 H8 exhibit

[H8 HDOS prompt] In 2013, I was asked by a local computer club to exhibit an early "homebrew" microcomputer from 1975-1978. Now, I don't like the term "homebrew", it sounds like something amateur and not-quite-serious. But their point was to show early microprocessor-based computers bought by individuals. The H-8 was a great candidate. So I pulled the system out for test and revival. It was of course still very clean. I powered it up gradually with the Variac, and found no immediate power problems. I got a nice enough display screen. I did the same with the H17 floppy drives, and did not see, hear, or smell any component failures.

[H8 keyboard]

[H8 baud rate]With the drives connected, I tried to operate the H8 as per the manual's instructions. The keyboard/display ROM monitor starts the boot process when a ROM floppy boot address is entered through the keyboard. A terminal must be connected to the console serial port, which was still marked with a label, and as I verified in the docs as the correct I/O address on the serial card. A simple LED serial tester showed transmit and recieve were connected OK. But I could not get the H8 to respond to the terminal - the monitor requires several "space" characters to establish the baud rate - note how the 7-segment display spells out "space".

[H8 handshake] After several tries and two terminals, I decided the problem was not the terminal, but might be the hardware handshaking between the computer and the terminal. One or both expected some RS-232 lines to be active when they were not (I'll not offer an explanation here, look up things like DTR/DSR and CTS/RTS). So I inserted a simple adapter that only connected transmit, receive and ground - that took care of the problem and the terminal and H8 communicated successfully.

Next I looked over the two 5.25-inch floppy drives in the H17 cabinet. With those cabled to the H8's floppy controller, the boot process clearly was trying to access the drives, but they were not responding "reasonably". Typically a floppy drive will seek to track 0, load heads, move from track to track. Instead the drive was seeking continuously. I switched the "drive select" jumpers to the other drive for drive 0. But that drive made a click-click noise per revolution which I did not like.

[H8 drive jam]Turned out the constant-seek drive had some debris which jammed the drive head. It performed a little better when the debris was removed. Better still, when I cleaned the connector to the flatcable from the H8 controller. As for the other drive, I determined that the rotating mech that inserts into the "hub" or center hole of the diskette, was the source of the noise. So putting that drive aside, I worked with the other drive, and got some results on the H8.

[H17 with Tandon drives] Once I saw some results, attempts to boot from floppy, I had to determine where the problem was: with the diskettes, the drive, the H8? Simplest thing to do was to verify the H8 floppy drive on another system. I have a Zenith Z-100 for drive repairs, and I determined the drive worked. But I am not confident in old single-sided drives. Also I did not have time or parts to repair the other drive. So I pulled two previously-tested Tandon TM-1002A drives, 35 track double sided, from my stock and after retesting them, I installed them in the H17. They look pretty good in the H-17 cabinet and are not unlike other drives available in the late 1970's.

[H8 HDOS prompt] [H8 HDOS prompt] So with good drives, and a bootable disk, I was able to get to the HDOS prompt. HDOS asks for an "action", such as "boot" which is followed by asking for the date (as shown in this paragraph). I had both HDOS 1.5 and 1.6 disks available; the 1.6 disk copy had more HDOS utility programs on it and was in better physical condition. So I "initialized" and then "copied" that disk as soon as I could. The amazing thing about HDOS and the H8, is how the H8 panel is used to display operations. In the photo of the H8 display in this paragraph, you can see how "copy" is displayed with a count of disk tracks. Many HDOS programs also display information on the H8 panel.

[H8 HDOS Adventure] Over a few hours' time, I worked enough with HDOS to get a little familiar with it, and by running these HDOS programs I more or less verified the H8 and two drives were operating reasonably. I wasn't sure how to demonstrate the H8 beyond running HDOS - certainly an alien OS to anyone under 40, and different even from CP/M. Then I found a disk marked "adventure" which also had HDOS on it. Adventure is a text-based game popular in the period; an exerpt of the dialog is on the screen image in this paragraph.

As of this date, I'm working on some paper documents to describe the H8, HDOS and Adventure as part of the exhibit I'm preparing for.

March 12-14th 2013

[H19 terminal] Since there's some fuss from MARCH about "100% working exhibits", I'm preparing some Plan B displays. Here's one of my H19 terminals. It's not the one that came with the H8, that one was bought some time later. This particular terminal was produced in Aug 1980 - a little past "1979" but let's see who picks a fight over this. H19's were first sold at least by 1979. Here's the H19 at 2400 baud on the startup of HDOS. Worked right away, last time I ran it must have been in 2009.

H8 resources

H8 manuals

A computer of the late 1970's had many kinds of documentation, especially a user-assembled or "kit" computer like the H-8. Each board, and the H8 with front panel & power supply & CPU board, had an "assembly" manual and a "operation" manual. Keep in mind, Heath sold KITS and these computers were bought to be assembled FROM COMPONENTS - resistors, IC's, etc. Heath was the "gold standard" for kit manuals that led you, part by part, through assembly and testing. The H8 and each card and each peripherals, like the H10 paper tape, the H17 floppy drives, and H9 and H19 terminals, had their own manuals. It adds up!

[H8 box o dox] 595-2013-02 H8 Assembly, 1977
595-2014-02 H8 Operation Manual
595-2028-01 H8-1 4K Static Memory H8-1
595-2033-02 H8 Parallel I/O Interface
595-2032-03 H8-5 Serial I/O and Cassette
595-2248-02 H8-4 Multiport serial I/O card Operation
595-2080-03 H8-4 Multiport serial I/O card Assembly
595-1996-04 H9 Video Terminal Assembly
595-2017-03 H9 Video Terminal Operation
595-1970-03 H10 Paper Tape Reader/Punch Assembly
595-2020-02 H10 Paper Tape Reader/Punch
595-2161 H17 Floppy Disk Assembly, 1978
595-2160 H17 Floppy Disk Operation, 1978.

Other companies produced H8 compatible cards. I have a few:

Trionyx Electronics, 64K memory for the H8
Morrow H8 extender card

Operating systems

As microcomputing technology advanced rapidly, year by year, in the mid-1970's, Heath/Zenith produced software and documentation to support advancing technology. Here's a list of what system software the H8 operated with, in chronological order.

1) The H-8 when first sold, ran on its own ROM monitor, which manages the octal keyboard, the LED display, and serial ports.

2) There are paper tape programs for text and program editing, assembly, BASIC. Often, paper tapes were read and written by a Model 33 Teletype. but Heath also had a H-10 papertape reader and punch.

3) there are cassette tape programs similar to the paper-tape programs. The Heath serial/cassette card reads and writes to audio cassette recorders of the 1970's. Yes, the same ones used to play music, were used for DATA and programs. This was common in the mid-1970's, when floppy drives were very expensive and used diskettes EIGHT inches in diameter.

4) Heath provided HDOS, their own operating system for the H8 and later the Z80 based H-89. This supports multiple floppy drives, which at that point were available as 5.25 inch. In its early versions the diskettes were hard-sectored, and the controller did not use what became LATER a 'standard', namely a floppy disk controller IC (FDC), a kind of microcontroller for floppy drives. Such chips did not exist when the H8 was first produced!

5) Heath later provided CP/M, an operating system from Digital Research which became the STANDARD for Intel 8-bit processor based microcomputers of the 1970's and into the 1980's.

For each bit of software, Heath provided a manual, or a chapter in a larger manual. Here's a partial list.

595-2169-01 H8-17 Software Reference Manual (diskette), 1978: op system, BUG, EDIT, ASM, BASIC
595-2048-02 H8 Software Reference Manual: (cassette), 1977: Op system, PAM-8, BUG-8, TED-8, HASL-8, BASIC

Heath Zenith computer clubs

1976 was decades before "the Internet". There were no computer stores (although Heathkit had some stores, as did other established companies which later made computers). Almost nobody OWNED a computer - a few people used them at work, for science and engineering and accounting. When microcomputers first came out - there was almost NO software. How did people get software? They wrote it themselves, sometimes hand-assembling on paper, and shared it with their local friends. (Or started companies, that's another story.)

How did they find each other? By forming computer clubs, which met monthly at varoius venues (libraries, schools, museums, homes). How did they stay in touch? They wrote and postal-mailed newsletters, on paper. HOw did they share software? They printed listings on paper, or traded paper-tapes, or cassettes, or diskettes. Clubs would form "software libraries" and copy or sell disks at meetings. Clubs would ask their own members to talk about hardware and software. Later, businesses would give talks at these meetings. Clubs also organized events, the first personal computer shows. Companies also organized clubs, like Heath's "HUG", the Heath User's Group.

I'll have images of some Heath computer club newsletters on this page soon. Newsletters I have include:

The BCS Update - a side publication of The Boston Computer Society for events and projects. BCS became nationally-known through the 1980's.
BUSS - the independent newsletter of Heath Co. Computers - a national group of Heath computer owners, developers, dealers, etc.
HUG Northshore - a Boston MA area club of Heath computerists, with a monthly newsletter

Computer magazines for home computing were scarce in the mid-1970's. They appeared quickly, however, as companies and people produced software, hardware, and wrote about it. A number of computer magazines were exclusive to Heath computers; REMARK and Sextant among others.

What happened to Heathkit?

Details on Heath/Zenith the company, are on my Heath-Zenith Web page.

Herb Johnson
New Jersey, USA
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Copyright © 2013 Herb Johnson