• Please review our updated Terms and Rules here

Cromemco Z-2D

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
Messages
1,389
Location
The Netherlands
Ooops I did it again... I could not resist to pick up this Cromemco with AMD-3A+ (And another dull terminal) nearby. The owner bought it somewhere in the eighties but never used the system. So it has been stored for over 35 years in his attic. Since they have to move to another house they had to let go of a lot of stuff, and also this machine...

I've powered up the ADM-3A+ on the variac and it just works fine. This is the 74LSxx series with cursor control and it is from 1980. My other ADM-3A is the older SN74xx model without cursor control. But that terminal is from 1981. So the older model is actually newer :)

The Cromemco itself was completely dead. That was caused by a broken fuse holder. I've seen this more often, people put a machine on its back and something snaps off. After replacing and also slowly powering it up it came to life. Sort of... The thing is that I didn't get any software with the machine. I tried to become a member of the Cromemco group, but for some reason I can't become a member there? You have to be invited?

I think my system is a very basic system. FCD controller, ZPU board, Memory board and a printer controller... But it would be helpful to know which exact disk images work on this machine...

Regards, Roland


Awake.jpg floppy controller.jpgfuse broken.jpgmemory.jpgpower 2.jpgpower.jpgprinter interface.jpgZPU.jpgdoor open.jpg
 

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,071
Location
UK - Worcester
Nice score! You have even got the drives...

You can request to become a member and it will happen...

You can also request access to the treasure trove of software disk images...

The 16FDC contains a basic ROM monitor that contains a test command so that you can test the memory out and exercise the drives.

You can boot CDOS and CP/M as 'Standard' for a Z80.

By improving the memory you can run Z80 Cromix (<=3 users) for a Z80 system...

If you let me know what ZPU, 64KZ and 16FDC configuration links and switches you have I can suggest how to proceed further.

Be aware (on power up) that you may have to hit <RETURN> a couple of times to get the RDOS ROM monitor prompt. This is the 'auto baud detection' mechanism (unless the terminal can automatically respond).

EDIT: I see it is set-up to AUTOBOOT. You should be able to switch the AUTOBOOT switch OFF and get it to enter the RDOS monitor. Check out the manual for the 16FDC.

Dave
 
Last edited:

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
Messages
1,389
Location
The Netherlands
Jos pointed me to http://dunfield.classiccmp.org/img42841/system.htm for the Cromemco disk images. I've written CDOS2585.IMD to a DSDD disk and it just boots after hitting enter... Never had such a boring system before... ;) :biggrin:

Cromemco draait.jpg

@Dave

These machines seem to be next level S100 systems... I mean: auto baud, self test in ROM, multi user...
Where do you see the autoboot switch? It that the red switch on the CPU board?
 
Last edited:

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,071
Location
UK - Worcester
No, it is a setting on the 16FDC disk controller (see http://dunfield.classiccmp.org/s100c/crom/16fdc.pdf switch position 3).

The RED switch on the CPU is 2/4 MHz clock select.

I may have a few spare cards left over after I have refurbished mine at some point in the future (e.g. D+7A) if you wanted to expand yours?

Yes, these things were built like 'tanks'...

Dave
 

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
Messages
1,389
Location
The Netherlands
Hi Dave, I have really no idea about what expansions are available. I've spoken to Oscar Vermeulen and he told me that I need more memory to run Cromix. Maybe I have to sit back and think about what I want and can do with the machine... :unsure:
 

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,071
Location
UK - Worcester
Yes, you need a 256KZ card as a minimum if I remember correctly. There is a multiuser BASIC available - but this also requires a number of 64KZ memory cards.

Anything multiuser just 'sucks' memory...

You will also require multiple serial ports (e.g. TUARTS) one for each 'user'.

I have about three full systems of Cromemco cards here - most of which require attention in some form or another. Unfortunately, the chassis were all thrown away (sad).

Dave
 

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
Messages
1,389
Location
The Netherlands
Hi Dave, thanks for the info. What would be the smallest update to be able to do more with the machine then just CP/M? I mean, I have enough CP/M and MP/M machines... And to be honest, the most have left the building in the past years... In my opinion if you know one, you know them all... :unsure:

So if the Z-2D can do more than CP/M - CDOS it might be a more interesting machine...
 

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,071
Location
UK - Worcester
With the ZPU, 16FDC and 64KZ cards there is nothing much more that can be done other than really run CDOS or CP/M...

As previously stated, to run Z80 Cromix will require additional serial cards and way more memory than you currently have.

A lot of Cromemco's ended up doing 'embedded' work - but these machines generally had way different cards than you have.

There are relay and opto-isolated digital input/output cards.
There are analogue/digital input/output cards.
There is the 'beautiful' Dazzler VDU interface card.
There are various EPROM cards (e.g. the Bytesaver).

A lot depends upon what you really want to do...

The Dazzler cards are very difficult to come across. They have been reverse engineered though by a VCFED member.

I have a DPU card - so a combined Z80/68K processor - and I am trying to port the Motorola 68K ECB 'Tutor' firmware over to it (see http://www.easy68k.com/paulrsm/mecb/mecb.htm) and (possibly) APL...

It would be nice to get some form of multitasking to work as well - but what... Still thinking about that one. I don't want to go too mad with the hardware...

Dave
 
Last edited:

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
Messages
1,389
Location
The Netherlands
Hi Dave,

Thanks for explaining. I don't want to do extreme things. Cromix would be fun, is it also possible to just add more memory and just use a single user setup with one serial card? Dazzler is fun too... I have to fix my 11/34 first which is filling up my desk, then all my DEC stuff is up and running... After that I might focus on the S100 systems I have... I have also a homebrew Altair and a Tei S100 machine... These deserve to run too... With this working Cromemco machine as a reference, things might become a bit easier...

Regards, Roland
 

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,071
Location
UK - Worcester
Yes, you will need to add more memory to run a single user Z80 Cromix. If using 64KZ cards I don't think this has been documented very well - but this is a hot topic on the cromemco google group at the moment...

In order to use Z80 Cromix - you have to use a minimum of a 16FDC (tick). You can use the 16FDC serial port as the first (only) serial port. I think (but I will confirm presently) that you will require two (2) 64KZ memory cards for a single-user Z80 Cromix system. Confirmed. One for the system and the other for the first (and only) user.

Dave
 
Last edited:

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
Messages
1,389
Location
The Netherlands
Hi Dave,

Adding just a 64KZ should not hurt that much I think. Wait... There is a 64KZ on Ebay now, but that board is more expensive then what I paid for my complete Cromemco including the ADM-3A+ and the other terminal together... :oops:

Maybe just place a modern replica memory board? Any replica's known to work in these Cromemco systems?

Regards, Roland
 

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,071
Location
UK - Worcester
The thing is the Cromemco bank switching.

I have the odd Comart memory card. So, yes, there are other cards (other than Cromemco) ones that will work.

Dave
 

MikeS

Veteran Member
Joined
Dec 23, 2005
Messages
7,493
Location
Toronto ON Canada
The thing is the Cromemco bank switching.

I have the odd Comart memory card. So, yes, there are other cards (other than Cromemco) ones that will work.

Dave
That's interesting. Tell me more about this Comart card; what size is it, and does it work in both Z80 and 68K mode? And what would be an example of the multitasking you mentioned?

Actually, Cromix (Z80 or 68K) with 64KZs and/or 256KZs is pretty well documented in the Cromix manual and the 64KZ and 256/1024KZ manuals. 64K per 'user' (max 6 for Z80) plus 64K for the system, where 'user' is a 'process', so you can actually run some processes concurrently as a single user.

It might be worth mentioning that even if you're running 68K Cromix you can still run CDOS and many CP/M programs as long as there's a Z80 _somewhere_ in the system.

And welcome to the arcane world of Cromemco, Roland; I'm trying to remember where I've run across your name often enough to actually remember it ;-)

While you're waiting to be accepted into the elite community with access to the Cromemco file and documentation GitHub, here's a Wayback link to an old but not really much out of date snapshot:

If Dave can't help you out with some compatible memory I might be able to help you out for somewhat less than that eBay item ;-)

Have FUN!

mike
 
Top