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Re: [N8VEM-S100:5861] Anyone have a working ZFDC with CPM3 and a 1.44MB drive?

I appreciate your suggestion -  I have tried a couple other CPU boards and get the same symptom, so maybe there is something about that System Support 1.    

So, as you suggested, the first thing I tried was to write to the floppy and then set the write protect tab.   

Now when I power off the system and power back on the diskette works.  So, you are correct - something is writing to that drive when the power is switched and the SS1 is a good suspect.

I have a Compupro Interfacer 4 that I can configure using the same ports without changing the bios so I will try that first.  I also have a IMSAI SIO but that will require bios changes.

Thanks so much for the suggestion as this is the first clue in many hours of tinkering.



On Friday, December 19, 2014 8:26:24 PM UTC-5, monahanz wrote:

That’s a strange one Thomas!  I suspect somehow you are getting a write glitch to the disk on power off or power on.  Can you setup everything as you have below, remove the disk. Power off, then power on and reinstall, does the problem occur, if not then do the same but use the disk write protect tab.  If all is OK then you need to track how/what is causing the disk write line to be activated. 


Are you absolutely sure there are no other boards/software writing to the ZFDC’s or IDE ports.  May want to change them in software/hardware and try that. A big step I know, but it could explain things.  I have all these boards except the SS Board1.  If anything I would suspect that board.  


Note that Cromemco ZPUZ does not support 16 bit port addressing (or > 64K RAM) , be sure all your boards have 8 bit only Ports.


Good luck






From: n8ve...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Thomas Owen
Sent: Friday, December 19, 2014 2:26 PM
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:5861] Anyone have a working ZFDC with CPM3 and a 1.44MB drive?




I am appealing to the Group once again as I am at a roadblock.   


My system is as follows:


Compupro CPUZ

Compupro System Support 1

Compupro Ram 17





The system boots CPM3 from the IDE CF board with drives A and B.  The ZFDC is configured as C and D with both drives being 1.44MB 3.5" floppies.


Here is what happens:


I can select, format and write to the floppy.

I can copy files to and from the floppy.


I can do anything I want, up to and including RESET of the system.


However, if I turn the power off and re-boot then the diskette previously written cannot be 'logged to'.  If I type C: I get an I/O error.

If I insert a diskette written on another system (like DOS) I can log to it just fine.


Even if I go back into the ZFDC Diags and set the drive format etc. it still fails.  It only works if I format the diskette and never power down.


So, the fact that the system will read a disk written under DOS tells me there must be something I am doing wrong in the write process that is not affected by a RESET, but is lost with POWER off.


Does anyone have this working and can offer any suggestions?


I have been over and over the BIOS code and can find nothing wrong.






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