cdos, Cromix and ram

[Endersending]

My journey with my IMSAI/Cromemco beast continues. I have recently aquired a 16FDC and some double sided shugart 850 floppy drives. I got tempted to try Cromix and quickly realized it wants more than 64K of ram.
Out all of the ram cards I have bought probably won't work with Cromix.
I am at a point where I am not sure the best route for the hardware I have. Here is a list of some of my hardware:
(3) 16KZ ram cards
(1) 64kz (piceeon brand)
(1) DMB 64K card (similar to 64KZ)
(1) 32K static Ram
a 16FDC, a 4FDC
(2) shugart 800/801 floppys in rackmount case
(2) shugart 850/851 floppys in rackmount case

I would like to try Cromix but I think I would have to invest in different RAM cards.
I would still like to be able to use the IMSAI front panel, which would require some static ram, so it would be nice to have a setup that has 32K static at 00H and then fill the rest with 16Kz boards.

I am seeking advice on with this hardware, what would you do?
Maybe the IMSAI should eventually have the 4FDC, single sided floppies and CDOS, and I could plan on building a newer system for cromix.

I have read that the 16KZ board are not compatible with Cromix. What boards are? From what I have read, the 64KZ board does not mention cromix. The Cromix manual says it supports 1024K Ram cards and cards that seem to be impossible to aquire.

Last question: From what I have read, CDOS can bank memory? Does CDOS automagically find all of the memory banks? Do I just start adding memory to banks and CDOS will detect it?

Thanks for the help!

 

[nullvalue]

Hey this is something I also recently tried. I have a Cromemco Z-2D system with ZPU and 16FDC. It runs CDOS great, but I have been unable to get Z-80 Cromix to boot on it at all. Keep in mind, there are 2 flavors of Cromix, Z80 version, and soon after, the Motorola 68x version. You didn't mention which CPU you have. I'd recommend checking out the Cromemco Google Group. Here's a recent thread detailing my own struggles to get it up and running - maybe something here might help you: https://groups.google.com/g/cromemco/c/0KwYKdQnBnU

BTW for Cromix you need a minimum of 128K in memory. 64K for System, and another 64K for each user (so, a minimum of one). While the static memory cards I have are supposed to be Cromix-compatible, I'm not having any luck getting it booted and am also thinking it's RAM-related. You mention the 64KZ cards (which I don't have, but should work with 2 of them properly configured). You can also look for a 256KZ which should work.

 

[Amardeep-AC9MF]

For Z80 Cromix (versions up to 11.27) you need a Z80 CPU, a 16FDC with modifications to support the Shugart drives, and a minimum of two 64KZ RAM cards. A TUART would be needed to support additional concurrent user logins as well as the required additional RAM banks.

There are no static RAM cards that fully support the port 40h bank switching scheme required by Cromix. There are several that claim to, but the ones I've looked at are incomplete implementations. You can use a 265KZ card with Z80 Cromix, but it requires a specific PROM to configure the bank switching appropriately.

CDOS is a 64KB operating system and to my knowledge (I may be wrong about this) does not make use of the bank switching available with multiple 64KZ memory cards.

 

[nullvalue]

For Z80 Cromix (versions up to 11.27) you need a Z80 CPU, a 16FDC with modifications to support the Shugart drives, and a minimum of two 64KZ RAM cards. A TUART would be needed to support additional concurrent user logins as well as the required additional RAM banks.

There are no static RAM cards that fully support the port 40h bank switching scheme required by Cromix. There are several that claim to, but the ones I've looked at are incomplete implementations. You can use a 265KZ card with Z80 Cromix, but it requires a specific PROM to configure the bank switching appropriately.

CDOS is a 64KB operating system and to my knowledge (I may be wrong about this) does not make use of the bank switching available with multiple 64KZ memory cards.

Amardeep, so in you opinion, (sorry, don't mean to hijack the thread) will this board not be compatible with Z80 Cromix? The manual has a section detailing how to set up multiples for Cromix System/User.

 

[Endersending]

All of my knowledge is for the Z80 version:
I also had to edit this a bunch because I was mixing the 16KZ with the 64KZ cards.

This confuses me even more and I guess I have to go reread some documentation.
This is what I have learned and please correct me because it sounds like I am wrong:
- There are 2 styles of Cromemco bank selection. we will call them an old and new style.
- CDOS would use the 'old style' that supports bank selection of 64K total, this is what 16KZ cards are for.
- Cromix uses a 'new style' the does NOT work with 16KZ cards.
- The 256KZ card ( are these even obtainable?) works with Cromix and not CDOS.

I believe this because I have a Measurement Systems DMB 6400 that states in the manual that is supports 7 bank selection, but to be used with Cromix, you have add add a daughter board that connects to the HD1, HD2 jumper blocks.
Link to daughter board manual

Also reading through the 16KZ manual there are no mentions of Cromix. I just looked at the manual - 64KZ is supported with Cromix
Which then leads me to believe CDOS does support some type of bank selection.

So I guess Cromix does a 32K page selection scheme (multi user) and CDOS does a 16K selection scheme (single user)

Please correct my limited knowledge and if someone could give an explanation or link to resources about how Cromemco did memory selection for CDOS and Cromix. Documentation about this is very vague.

 

[nullvalue]

As far as using multiple 16KZ's in CDOS, it's not really bank selection, so much as "where in the 64 KB of addressable memory does each 16KZ reside". The 16KZ can be jumpered to sit in 4 different locations of memory. If you jumper them correct, 4 16KZ cards can be configured to fill all 64KB. This is not really the same thing as bank addressing, which allows you to go past that 64KB limit within operating systems that support it.

 

[Endersending]

So CDOS can not and was never designed to use more than 64K of ram?
Can Cromix use 16KZ cards?

 

[nullvalue]

So CDOS can not and was never designed to use more than 64K of ram?

No I don't believe it's possible.

Can Cromix use 16KZ cards?

No I don't thinks so. Looking at the 16KZ manual, it does appear to be capable of responding to the port 40h bank switching - but I'm pretty sure Cromix has a requirement that each bank/block be at least 32KB. I honestly don't know what the point of it was since the OS didn't natively support it - i guess it would be up to you to code your own software to do the bank switching.

 

[hmb]

So CDOS can not and was never designed to use more than 64K of ram?
Can Cromix use 16KZ cards?

It's complicated. The 64KZ RAM board instruction manual provides a very detailed description of several scenarios under which a Cromemco system running CDOS can make use of multiple banks of RAM made up of 16KZ and 64KZ boards. The "typical user" would normally just run CDOS in a single 64K bank made up of one 64KZ or four 16KZ RAM boards.

For Z80 Cromix, you need to consult the Cromix System Administrator's Manual, which goes into some detail on memory requirements and memory allocation. The minimum requirement to run Z80 Cromix is two 64KZ-II RevD boards. The 16KZ and original 64KZ RAM boards are not in the "supported list".

Indeed 64KZ-II, but especially 256KZ and 1024KZ RAM boards, are not easy to acquire. These boards were usually only found in Cromemco's high end business systems, and likely most were disposed of rather than ending up in the hands of hobbyists after they were retired.

 

[nullvalue]

The minimum requirement to run Z80 Cromix is two 64KZ-II RevD boards. The 16KZ and original 64KZ RAM boards are not in the "supported list"

Oh wow I didn't realize the original 64KZ wasn't even supported. Besides the 64KZ-II, 256KZ & 1024KZ, are there any other supported boards for Z80 Cromix?

Ah just found that section in the manual, 512MSU also supported but only for 68000.

 

[hmb]

Oh wow I didn't realize the original 64KZ wasn't even supported. Besides the 64KZ-II, 256KZ & 1024KZ, are there any other supported boards for Z80 Cromix?

Ah just found that section in the manual, 512MSU also supported but only for 68000.

The 256MSU and 512MSU boards are very rare, and either of them needs to be paired with the MCU board that performs the actual error detection and correction.

I am not aware of any third-party RAM boards that worked with Z80 Cromix. My guess is that if any existed, they would be as uncommon as Cromemco's own versions.

 

[Amardeep-AC9MF]

The 256MSU and 512MSU boards are very rare, and either of them needs to be paired with the MCU board that performs the actual error detection and correction.

I am not aware of any third-party RAM boards that worked with Z80 Cromix. My guess is that if any existed, they would be as uncommon as Cromemco's own versions.

Are you certain 64KZ are not supported by Z80 Cromix? Mine seem to work fine. Back in the day my 11.27 system ran on a set of CCS 2066 boards. I have only ever owned one 64KZ-II which was that awful early revision B board that got bounced around between several people and the seller last year. The one with the missing delay line and no documentation.

 

[Amardeep-AC9MF]

Amardeep, so in you opinion, (sorry, don't mean to hijack the thread) will this board not be compatible with Z80 Cromix? The manual has a section detailing how to set up multiples for Cromix System/User.

Actually I think that board is the only static RAM board I've seen that will work (it is new to me). It fully implements the bank assignment for all eight positions including the ability to always map the high bank for all boards in the system when bit 7 is selected.

 

[hmb]

Are you certain 64KZ are not supported by Z80 Cromix? Mine seem to work fine. Back in the day my 11.27 system ran on a set of CCS 2066 boards. I have only ever owned one 64KZ-II which was that awful early revision B board that got bounced around between several people and the seller last year. The one with the missing delay line and no documentation.

I just quoted what the Z80 Cromix Admin Manual said. Perhaps it was a later version published after the original 64KZ had been discontinued, and Cromemco was just targeting "new owners" with their manual.

 

[hmb]

Are you certain 64KZ are not supported by Z80 Cromix? Mine seem to work fine. Back in the day my 11.27 system ran on a set of CCS 2066 boards. I have only ever owned one 64KZ-II which was that awful early revision B board that got bounced around between several people and the seller last year. The one with the missing delay line and no documentation.

I found an older (1980) version of the Cromix manual which only describes use of the 64KZ and no other RAM boards - which matches your experience.

 

[Endersending]

I am able to boot cromix with this PIICEON card, but I cannot login because I don't have another card, only 16Kz's and the DMB 6400 which is missing a modification for cromix.
As much as I want to run Cromix, maybe the IMSAI should use the 16KZ with some static ram and someday maybe I will come across a system one with some ram in it.

 

[Endersending]

I have been reading some more and I am still confused.
Looking in the 64KZ manual, it shows how to use 16KZ cards with it (banking up to 512K), but does not talk about what operating system. is it possible this is just a theory if people wanted to create their own bank selection? I guess they are alluding to Cromix
CDOS manuals say nothing about bank selection.
It sounds like there is a 3rd contender: multi-user Basic - you need 32K for the OS and 32K for each user (6 users total). I think this is a stand-alone Operating system (not CDOS not CROMIX). This afternoon I am going to go through documents and notes and see if I can get Cromix to work with the 16KZ cards I have.
I will post more because this is not over.
Page 20 of 64KZ PDF talks about 16KZ 64KZ bank selection. I have only see mention of CDOS.
I feel like CDOS can handle more than 64K, but only single user?

 

[Endersending]

I have figured out what I wanted to know. Everything has been revealed in the Multi-User Basic manual.
This manual describes a multi user CDOS version that uses the 64Kz and 16Kz cars with bank selection to run up to 6 users in a CDOS like OS.
Has anyone used MU Basic? After I get signed up to google groups/cromemco github and acquire the software I will try it out.
this is very exciting. The MU Basic OS manual states you can run 16K basic (shared executable?) to all users or each user can run their own program.