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Any Heathkit/Zenith H/Z-90 owners?

NobodyIsHere

Veteran Member
Joined
Dec 21, 2006
Messages
2,403
Hi,
Are there any Heathkit/Zenith H/Z-90 owners here? I recently restored one and have found there are few if any resources online. There is some documentation mixed in with the H/Z-89 archives but nothing in the way of disk images, etc. I have some items including a couple of boot disk images.

Please let me know if anyone is interested. Thanks!

Andrew Lynch
 
AJ,

Last time I looked, there were plenty of Z-90 resources available on daNet (including HUG). Have you tried alt.comp.zenith? There's also 'Doc Shipley' on Compuserve. Holla at me if you need more info...

--T
 
AJ,

Last time I looked, there were plenty of Z-90 resources available on daNet (including HUG). Have you tried alt.comp.zenith? There's also 'Doc Shipley' on Compuserve. Holla at me if you need more info...

--T


Hi Terry,
I have had no luck finding much of anything. All I have found is the SEBHC.ORG site and I have joined the mailing list. Also, there is a Z-100 lifeline site. There aren't any disk image archives I have been able to find.

Do you know of any good links? I have Google'd quite a bit and found virtually nothing on the Z-90.

Thanks!

Andrew Lynch
 
MeToo, but there is still comp.sys.zenith.z100, AFAIK. It was fairly active a couple years ago, with much info on the Z-90 (89) series. The best source is still Doc, on CompuServe. If there's anything to be known, he knows it (former Zenith techie). Try there. You'll have to register for a free account, but after that, look under the vintage computing forums, Zenith, and he's not hard to find. From my experience, he's more than happy to share whatever he knows with anyone interested enough to ask.

As for freeware. I'd have to track down the link, but the HUG archives are somewhere on the net, last I knew (couple years ago).

--T
 
IIRC, the Z-90 was just a factory assembled H/Z-89. My memory is a little fuzzy at the moment (Fat Tuesday), but ISTR the Z-90 having a couple of S-100 slots, and I'm absolutely certain that the (89) bootdisks won't boot the Z-90, but after CP/M is loaded, the transient software is compatible.

--T
 
Very fuzzy indeed, Terry! :)

The H-89/Z-90 doesn't have any S-100 slots at all. Also, you can freely mix and match H-89/Z-90 software as you like. The hardware is 100% compatible. You can run both HDOS and CP/M on either machine. The only caveat you have to worry about is the disk controllers.

The H-17 disk controller that is found in most machines is a hard sectored controller and will only work with hard sectored media. The soft sectored controller is known as the H-37 and can be easily spotted by the WD 1797 FDC that is on the board.

The only real difference between the '89 and '90 is that the "Zenith" models were factory assembled and the "Heathkit" models were built by the end-user.

An interesting note - the H-89 is actually an H-19 serial terminal! If you look inside an H-89 or Z-90, you'll see two circuit boards held in a steel frame at the back of the case. The "front" circuit board is the "89" part. It's got the bus connectors on it for up to 5 expansion cards and a 16K memory card. The board behind it is actually an H-19 terminal board. The two boards are connected together via a small harness and all they do is pass power & serial signals. The keyboard is also connected to the '19 board. You can easily turn a dead '89 that has a working terminal board back into an H-19 by connecting one of the back DE25 connectors to the '19 board.

g.
 
Hi Gene,
I do have a couple of boot disks for the Z-90 but given the scarcity of disk images available for this platform, I am considering "retrofitting" the Z-90 with the Zenith hard sector controller and going backward to a Z-89 configuration. There seems to be TONS of H/Z-89 disk images available on sebhc.org. Strange, you'd think the Z-90 disk format would be easier as it is soft sector versus the hard sector H/Z-89 disks.

You just never can tell, I guess.

Thanks!

Andrew Lynch
 
Hi
The softsectored controller was more rare. Most Z-90's used the
hard sectored as well. The Z-90 did come with the CP/M compatable
address decoder as well as the additional expansion RAM. Other
than that, it was still a H89.
As you discovered, there were additional monitor instructions
as well.
The hard sectored images are a little more difficult to use
because you need to use a serial connection and run in a
true DOS ( not windows DOS ).
I wrote the transfer programs a few years back.
The soft sectored disk are easier to deal with. Especially
now that Dave's tool can take other common formats.
Dwight
 
Hi
I thought I'd note that one could use most applications from
a hard sectored image and transfer it to a softsectored image
and then use that. At least that is my understanding.
The directory structures are the same as I understand. I've
done this on other machines where I create the image from the
files and then transfer that image to the target disk ( on a M20
olivetti ). I've not looked into the HDOS directory structures
but I don't think it wouldn't be too difficult as it is documented
someplace.
Dwight
 
Hi
It was always an option. For applications that used CP/M,
most wanted the soft sectored ( one could still do CP/M in
hardsectored but exchange to other systems was troubled ).
If you mainly intended to use HDOS, most stayed with the
hardsectored. I have a Z-90 that I've not had time to fiddle with
that has hardsectored. At least one other that I know of
is also hardsectored. I'm relatively sure that this was
still an upgrade to get softsectored on the Z-90 as well.
Dwight
 
! have a Z-89/90 (not sure which, could never find any model #) It alas sits unressurected (sigh ) like too many of my beasts :^{ . I've also an H-77. I found them outside a church in downtown Toronto and suspect they were from the 1982 Canadian Mt. Everest Expedition. The H-77 has an official sticker on it from the time.

IIRC one of the strange things with it was that it seemed to have a sound card. It's been many years since I've opened it. Perhaps some relationship to the cassette connector on the back ? Should I ever get thru my lengthy to-do list I'll spend some time on it. Nice to know there are now disk images available for it, and also the manual.

Lawrence
 
Hi,

One idea I have been batting around inside my head is that since FDCs are open collector devices, and the Z-90 already has a soft sector FDC installed, is that I could just install another hard sector FDC right along side it.

The Z-37 manual does speak of a dual hard/soft sectored Z-90 configuration so I suspect it is possible. Since only a single full height floppy is installed, I would have to make a special cable with two 34 pin female IDC headers on it so it could plug into both FDCs at the same time.

As both FDCs are open collector, I doubt either FDC will care if the other is doing something. With a single tasking OS like CP/M or HDOS the likelihood of a simultaneous dual access is pretty much nil.

Or so the theory goes. Does that sound even plausible?

Thanks!

Andrew Lynch
 
Hi
I suspect it would work. You couldn't do two drives
because after selecting a drive the drive select line
is usually left selected. One control would be drive
0 while the other would be drive 1. Both select lines
at the same time.
Of course, if you are only using a single drive, it should be
fine. I don't recall what address is decoded by the soft sectored.
Dwight
 
AJ,

The H/Z-89/90? that I used to have did have two fd controllers, one for the internal hs, and a separate one with external connector for the soft-sector drives (and it could handle 96-tpi), and I can confirm that they all three did work together. I sold that machine to ziloo, so mebbe he can fill in some more info that my data-retrieval system is not finding just now, since he has the fdc in hand.

--T
 
I'm a bit surprised that no one emmited a "scoff" on the concept that a Z-89/90 could possibly have a sound card, much before before the adlib or soundblaster cards, most of which also required a memory upgrade. I brought this up to Tony Duehl on classic comp and he provided me an explanation at that time. I'm sure it is there in the archives. I will eventually open up the Z89/90 again at some point and describe the card which IIRC was connected to the Terminal board. And should any "electronic engineers" doubt my statements, will also do pictures of what I see as a certified Digital ElectronicTechnician.

If this was indeed the computer the Canadian Everest 82 Expedition took with them, it would have been of high quality components not normally found in consumer electronics. Not hard to deduce by most of the non-scientific public.

My general attitude to engineers, and 2 of my brothers were such, is they propound ideas based on hypotheses and then leave it to the technicians to make them look good, since few of them, except in Lab 101, have ever held a test device.

Lawrence
 
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AJ,

The H/Z-89/90? that I used to have did have two fd controllers, one for the internal hs, and a separate one with external connector for the soft-sector drives (and it could handle 96-tpi), and I can confirm that they all three did work together. I sold that machine to ziloo, so mebbe he can fill in some more info that my data-retrieval system is not finding just now, since he has the fdc in hand.
--T



Hi
Yes, one could connect multiple drives. What was being talked about was
using the same drive on multiple controllers.
The 96 tpi disk were used with the hard sectored controller as well as the
soft sectored. I have several disk that were 96 tpi but I've never connected
a drive up to try them.
Dwight
 
... IIRC one of the strange things with it was that it seemed to have a sound card. It's been many years since I've opened it. Perhaps some relationship to the cassette connector on the back ? Should I ever get thru my lengthy to-do list I'll spend some time on it. Nice to know there are now disk images available for it, and also the manual.

Lawrence

What you have is a cassette interface board, which was used for storing/retrieving data off of audio cassettes.

The H-88 was the computer shipped with just the cassette interface board, and anywhere from 16K to 48K of RAM.

The H/Z-89 was the computer shipped with an H-17 hard sectored disk controller card. The H/Z-90 (don't recall if the kit version used the -90 or not) would have included the H/Z-37 soft sectored controller board, which would work with single or double sided 40 or 96tpi drives. Somewhere in the mix was also a new set of relocating ROMs that moved the bootloader to high RAM so the OS could load at 0x0000; this was necessary for CP/M to run unmodified applications (which expected a jump table at 0x0000 and a program start at 0x0100).

As an aside, someone once published a hacked CP/M BIOS which allowed the hard sectored controller to run 96tpi drives, though finding compatible media was a bit of an adventure!

Heath also came out with the H/Z-47 8" controller, which could run 1 or 2 single or doublesided 8" floppies; there was also the H/Z-67 Winchester controller, which ran a dedicated subsystem containing an 8" floppy and an 8" hard drive.

A couple of other firms, Magnolia and CDR, also put out soft-sectored 5-1/4 controllers; the CDR card could also, if memory serves, control 8" drives.

There were also software and hardware hacks to get the H/Z-37 to work with 4MHz and 6MHz CPU upgrades, and to get the 37 to address 4 drives (it could only do 3 with a stock BIOS).

My favorite goody was the CDR RAMdisk card, which let you stuff a palatial 1MB of RAM in the machine and treat it as a 900KB RAMdisk; you could even hard reset the box and reboot off it! So long as the power didn't glitch (a big if in Florida!) that gizmo made the 89 the next best thing to instant in response.

Alas, my 89 CPU eventually succumbed to a lightning strike. The machine still lives on, however, with an Ampro LittleBoard+ and a 100MB SCSI hard drive. Gotta have that green screen to play Adventure!

http://www.afn.org/~scotsman/photos/h89.and.toaster.oven.jpg
 
The H/Z-89/90? that I used to have did have two fd controllers, .... I sold that machine to ziloo, so mebbe he can fill in some more info .....
--T

Well ...... about a year ago, I purchased a H/Z 89/90 from Terry,
but since I am on this side of the waters and that system needed
some tweaking, I asked Terry to kindly mail it to a fellow by the name
Lee Heart who is a H/Z system guru. He was a frequent contributor to
SEBHC group, and I haven't heard from him for sometimes now. So...no,
sorry but I can't help you there.

There is lots of information about H/Z system and peripherals on SEBHC archives.

ziloo
 
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