Subject: Re: H89 CP/M hard-secored boot diskette

From: "Dwight K. Elvey" <[email-masked]>
Date: Fri Apr 4 12:37:42 2003

>From: [email-masked]
>
>> MTR-90 is in the ROM on the 89's CPU board.  My MTR-90 manual indicates
>
>[...]
>
>> It certainly seems as if you can run both controllers in one machine.
>
>You most certainly can. My Z90 (essentially the same machine -- AFAIK the 
>differences are that it came fully assembled ('Z', not 'H'), and came 
>with 64K RAM, has MTR-90, the hard sector controller and the 
>double-density soft sector controller. The former is cabled to the single 
>built-in drive, the latter to an external drive box.
>
>It will boot either HDOS or CP/M, and can use both types of disks
>
>-tony
>

 The Z90 is built to be 64K a H89 isn't. As far
as I recall, the H89 took more than a simple jumper or
switch to make it CP/M compatable.
 Also, one should note that HDOS came in both hard and soft sectored.
Dwight

---

From: "Patrick Rigney" <[email-masked]>
Date: Fri Apr 4 12:38:09 2003

>  Also, one should note that HDOS came in both hard and soft sectored.

Dwight, I think you're right.  Address decode is controlled by U516 and U517
on the CPU board... and those are PROMs of Heath's creation... close to
unobtainium.  I have several different versions of each of these PROMs, but
I haven't yet figured out their contents and differences.

Oh, and regarding my earlier comment about the MTR EPROM... I went back and
looked at my old emails, and apparently there's more to the MTR-90 ROM
version story.  You can use either 444-142 *or* 444-84 with the soft-sector
controller.  Version 444-142 is reported to support both 40 and 80 track
drives; 444-84 supports only 40 track drives.

Tony, out of curiousity, what are your versions of the various PROMs and
EPROMs at U516, 517, 518, and 520 on your Z90?

Patrick

---

From: [email-masked] (Tony Duell)
Date: Fri Apr 4 12:38:17 2003

> on the CPU board... and those are PROMs of Heath's creation... close to

I have, of course, dumps of the 2 proms (one is 32*8, the other 256*4) in 
my Z90. They're a lot less 'unobtainium' than many chips I deal with!.

> I haven't yet figured out their contents and differences.

IIRC, there were modified PROMs for CP/M-capable machines, which allowed 
the memory to be re-mapped with RAM at address 0. Older version CPU 
boards need a jumper wire (from an output port bit to a pin on the PROM, 
basically) for this, I think it's a trace on later boards.

> EPROMs at U516, 517, 518, and 520 on your Z90?

That would involve getting to the Z90, which is not going to be trivial....

-tony

---

From: "Patrick Rigney" <[email-masked]>
Date: Fri Apr 4 12:38:21 2003

> my Z90. They're a lot less 'unobtainium' than many chips I deal with!.

That's good news, because I have a few CPU boards I'd like to upgrade... so,
modern equivalent blanks are available?  I haven't ripped labels off of any
of them to see what they really are.

> That would involve getting to the Z90, which is not going to be

LOL!  Sure, just curious.  I want to confirm my suspicions that this '89 I'm
using has been upgraded to the equivalent of your '90, but I'll take it on
faith.  If I can get that soft-sectored controller going, then it's
equivalent enough for me.  But hey, wasn't this the thread where two days
ago, everyone was talking about how easy it was to open cases and build
cables? ;-)

Patrick

---

From: "Eric Smith" <[email-masked]>
Date: Fri Apr 4 12:38:24 2003

>> I have, of course, dumps of the 2 proms (one is 32*8, the other 256*4)
>> in my Z90. They're a lot less 'unobtainium' than many chips I deal
>> with!.
>
> That's good news, because I have a few CPU boards I'd like to upgrade...
> so, modern equivalent blanks are available?  I haven't ripped labels off
> of any of them to see what they really are.

No, there are basically no modern equivalents for those parts.
Cypress makes some CMOS PROM and EPROM parts for bipolar replacement,
but not in those small sizes, and the ones that they do make are
extremely expensive.  And it looks like they're phasing out the windowed
(erasable) parts.

If you need to replace those parts, you'll have to buy surplus or
NOS (new old stock) parts.

---

From: "Patrick Rigney" <[email-masked]>
Date: Fri Apr 4 12:39:02 2003

> > That would involve getting to the Z90, which is not going to be

FYI, I found this while trolling through some links on retroarchive.org.
Excerpt (edited) from an Arpanet message dated 17-feb-1984:

"When I ordered CP/M the first time and it didn't work, I called
Heath and they said "Oh, yeah, you need a hardware upgrade!"
So I did the following:

1) Replaced the 444-42 in U517 with a 444-66
2) Connect a jumper from the middle pin of U503 to pin 17 of P509
They assured me this would work.  However, to make the full upgrade,
I could also do:
3) Replace the 444-40 in U518 with a 444-62
4) Replace the 444-43 in U550 with a 444-61
If I did this, I would lose cassette capability.  Since this wasn't
necessary (they said) I decided to just do 1 & 2.

When I did this and it still didn't work, I called Heath again.  They
said it should have worked and my disk must be bad.  So they sent me
a new disk..guess what, still didn't work.  Then they say hardware
problem with the disk drive.  That's when I put my problem on the net.
Mr. D. C. Finch of Phoenix was kind enough to write me a letter
(they have R/O access to the net) which told me that indeed 3 & 4
were necessary (at least for CP/M 2.2.03 and later).  So this morning
I called Heath again and they said, "That's right, you have to replace
all three chips!"  Just wish they had said that back in November!!
I'll be happy to give anyone the details of Mr. Finch's letter if
asked, I don't think most people are that interested.

---

From: [email-masked] (Tony Duell)
Date: Mon Apr 7 12:40:15 2003

> of them to see what they really are.

They _were_ standard PROMs, but I think that blanks are going to be 
rather hard to find now. There must be something that can be kludged in, 
though.

> ago, everyone was talking about how easy it was to open cases and build

If I could get to the machine, it would be trivial to pull the boards 
(I've taken this machine totally apart in the past, and can remember how 
to do it). The problem is that there's a lot of stuff between me and the 
Z90...

-tony