[Coco] Making model1 physical disks

John E. Malmberg wb8tyw at qsl.net
Sun May 3 08:58:29 EDT 2020

On 5/2/2020 9:15 PM, rietveld rietveld wrote:
> Not coco but still radioshack related. I was hoping someone here can help
> I am trying to make physical model 1(not coco1) disks  ‎using a Tandy 1000 (286).
> The Tandy 1000 is running DOS 6.22 from C: DRIVE (cf card) and has a
> physical 5 1/4 floppy. ‎ ‎I am using a Model 1 emulator on my win10
> laptop to ‎create a virtual. Dsk. by adding /CMD files. I then copy
> that. Dsk onto my CF card.   I can't seem to do a COPY *.* from C
> drive (cf card) to B drive (5 1/4)

More specific information is needed for your post.

Since you state you are booted from the C: CF card, I am assuming that 
you are adding the disk image from the CF card to the Tandy 1000.

As I recall, 286 system generally came with a 5.25 inch high density 
floppy disks, but it appears that the Tandy 1000 used double density 
double sided disks.

What program are you trying to use to transfer the disk image from the 
CF card to the floppy?

There is nothing native to MS-DOS that can read or write a disk image to 
floppy that I am aware of for even normal MS-DOS floppies.

If you are trying to write your own, or adapt a COCO related program, 
there is a wrinkle to be aware of.

I do not know much about a model I TRSDOS, but I would assume that a 
model III original TRSDOS behaved the same way.

TRS-80 Model III TRSDOS marks the directory sectors with a deleted 
address mark.  That is how it finds where the directory is on the disk.

A disk image for a Model I/III emulator that would need some way to 
indicate that deleted address mark on a sector, so it would not be a 
sector by sector disk image.  The emulator documentation should document 
this format.

MS-DOS treats that as a bad sector when reading, and I do not think it 
can write a single sector with a deleted address mark.  I never found a 
way around that.

At one point I was trying to adapt my cocodisk program to read TRSDOS 

I suspected that the read track at once or write track at once might 
work as the controller should ignore the sector information.  I never 
got around to trying that.

I do not know if your transfer program has a solution to that issue.

I think that later versions of LDOS for the model III/IV stopped using 
the deleted address mark.  So an emulator could produce a disk image 
that contains only sectors.  Those disk images would not support disks 
with copy protection on them.

The CoCo SDC manual at https://goo.gl/bZ9ebS documents various floppy 
image disk image formats.

I am not sure if a the CoCo ROM disk basic can read a sector with a 
deleted address mark.  I never tried it.

So I do not know if there are any utilities for the COCO that can read 
or write a TRS-DOS or LDOS floppy disk.


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