My new System 3 and Z-2D

[Claudio Grossi]

Here are a couple of Cromemco systems I bought 2 weeks ago. Thanks to a mate who does transport I was able to get them safely to my door step in Brisbane from Newcastle (about 800km / 500 miles) in a few days from committing to them.

 

The System 3 is in very good condition but the Z-2D is a bit rough and appears to have been weathered a little. Came with around 200 x 8" Floppy Disks, manuals and an external dual 5 1/4" floppy unit. The System 3 had ZPU, 16FDC, 64KZ, PRI & TU-ART cards installed. There were 10 x loose S-100 cards, some most likely from the Z-2D as it was empty. They included 2 x ZPU's, 16FDC, 4FDC, TU-ART, PRI, various RAM cards and bus extender card.

 

I spent a little bit of time tidying them up with not much needing done to the System 3 but the Z-2D had sound insulation foam inside the cabinet which had perished so that was all vacuumed out. The power supply on the back panel had nothing holding it in place so unfortunately it caused a little damage to the S-100 backplane but should be simple to repair. So I temporarily secured it in place and will be getting some new hardware to tidy it all up

 

A local friend was keen and kind enough to help check these out and get them slowly powered up with a variac. So a few days ago we started on the System 3. After a bit of testing and checking, we discovered the front panel key switch needed some contact cleaner, 1 of the S-100 slots had a broken pin that was shorting a power rail, and the 2 bridge rectifiers in the power supply were replaced. The empty chassis then powered up fine.

 

Next the board set was tested starting with the ZPU, then 64KZ RAM board and 16FDC. Most seemed OK but we still couldn't boot into RDOS. I left the system with my friend and he worked his magic and sorted out some issues on one of the RAM boards, dumped the RDOS 2.01 ROM after making an adapter and got it booting OK.

 

Once I get the system back I'll try and get it going with a Gotek then tackle the Persci 299B dual 8" Floppy Drive and external dual 5 1/4" drives.

 

He also tested out a basic board set for the Z-2D (ZPU, RAM & 16FDC) and was able to get them going. The Z-2D will be a project I will tackle when time permits and I get myself a variac.

 

The documentation included the original QA document for the System 3 build from the factory and amazingly it was performed EXACTLY 43 years from the day I had it delivered to me in Brisbane!

[Claudio Grossi]

OK, so made some progress today after picking up the System 3

1. It still works as my friend had it going with booting to RDOS - well done 

2. I connected the dual 5 1/4" external floppy drives (Mr Floppy) and they seemed to work but I don't have any 5 1/4" Cromemco boot disks (yet) so tried my Kaypro ones and even though the system tried to boot (I heard seeking noises), it failed to boot which is no surprise (I think)

3. I was getting ready to setup a Gotek and then decided to try out the Persci drive. After a bit of trial and error reconnecting it, I finally got it to load an 8" Floppy (it has a motorised engage once you push the disk in all the way) and it unloads when you press the A button on front panel, but it didn't seem to seek when I tried to boot. So need to check jumpers, etc to make sure the system is setup to boot from 8" drive.

4. Then moved back to the Gotek and after more trial and error I got the Gotek going but haven't been able to get it to boot so need to check disk image formats and make sure they match the config file for density, etc.

Pretty happy with the progress to date.

[Claudio Grossi]

Well Graham Lees sent me a working disk image as (CDOS HFE format from the Cromemco Github repository) and I was having a similar issue (hanging at Standby prompt). Was about to try another 16FDC and decided to try setting the switches on 16FDC to Auto Boot (switch 2 and 3 from top to on) and it freakin worked!! Not sure why it wouldn't manually boot but will figure it out another day. Thanks again Graham.

Next job, get the Persci working :)

[Claudio Grossi]

Wondering what determines the initial drive assignment when connecting 8" and 5 1/4" drives to the 16FDC currently running RDOS 2.01?

When I connect my Gotek to the 34 pin 5 1/4" connector on the 16FDC, it boots and is assigned drive A. If I also have the 8" drive connected (Persci) to the 50 pin connector, it is assigned drive C and does seek but comes up with 'Disk not ready' but could be because CDOS is configured to see another 5 1/4" drive or the drive is faulty.

If I just connect the 8" drive and try and boot the disk drive doesn't even seek so not sure if it still thinks the 8" drive is drive C and is not the boot device or if there is something else going on.

I intend to upgrade RDOS to at least 2.5x but need a ROM adapter or original ROM to make that happen.

[Mike Arnold]

Claudio, the drive assignment is half software and half hardware. As you know, the jumpers on the drive itself determines which drive address it responds to. When you generate CDOS you define what drive type is where (DS0, DS1, DS2, DS3 = A: B: C: D:). Connecting an 8in when CDOS is expecting 5.25in (or vice versa) will cause a failure. In other words, you need to know how CDOS is configured before you set the hardware up. I cannot remember how to tell how CDOS is configured. I think that STAT tells you but if the drive is not behaving then I am not sure you will get anything. 

If you configure CDOS for an 8in Persci you cannot use a Tandon, whereas if you configure CDOS for a Tandon you can use a Persci provided you do not try to use both halves of the Persci (seeking gets messed up). Obviously, the 50w pin-out needs to be correct.

Finally, you could check on the modification level for your 16FDC. The Persci 50w interface differs from the Tandon on a few pins. The 16FDC was designed for a Persci pin-out whereas the 64FDC is for a Tandon. There was a mod. to switch certain pins on a 16FDC so that it could drive a Tandon. You may have one of these boards.

Mike

[Udo Munk]

The stat command reports the drive configuration as well as the disk format in the drive. Running stat on a drive where the floppy disk cannot be read results in an error.

A.stat b:
STAT (System Status) version 02.22    

Drive B not ready

B.

[jima]

With apologies for jacking the thread, but does anyone have a link to the mod for the 16FDC to drive TM848 drives? I have a pair of 'like new' TM848-02 drives I would like to get operational and all the info I can find relates to Shugart and Qume drives or to cable mods.

James

[Peter Higgins]

The Tandon TM848-2 uses the same interface as a Shugart SA-800, therefore you can follow the detailed instructions provided here:

http://www.retrotechnology.com/herbs_stuff/16fdc.html

http://www.retrotechnology.com/herbs_stuff/16FDC_ModsForShugart.txt

On the TM848-2's you need to set the drive select jumper, with one set to DS1 and the other set to DS2 - same as on all Shugart and Qume drives.

The TM848-2 was designed with a few features that are similar to newer 5.25" drives designed around the same time. The spindle motor is DC-powered (unlike the always-on AC motors on older Shugart and Qume 8" drives) and with jumpers on the drive set as shipped the spindle motor on the TM848-2 will turn on only when the drive is selected. The TM848-2 has no "head load" solenoid - the read/write head on these drives is always "loaded" to the disk surface when there is a disk in the drive and the disk lock lever has been turned "on".

[Ralf Stein]

Lots of info about 16/64FDCs & 8" drives out there, including this:

https://groups.google.com/g/comp.os.cpm/c/2p0O6xRqXMw/m/NtAIKAb-6FUJ?pli=1

Amardeep did a pretty good job documenting things.

Herb's site also has some good info.

Somewhere there's also info about Perscis and Tandons on the same cable.

(Another) Mike

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[Claudio Grossi]

Thanks Udo and Mike. I'm dealing with a slight issue with my Gotek then I will try a few things such as modify CDOS drive assignment details and see if I can at least get to read the 8" drive then try and boot off it.

[jima]

Many thanks to Peter and (Another) Mike :) - looks like just what I need.

James