[Coco] Determining OS-9 Floppy Type

[Joel Ewy]

I'm fairly sure that the 40 track DSDD descriptor will actually read and
write 35 track disks.  At least I don't remember having to use dmode to
read the old original  RS distribution disks. 

If my recollection is correct, then all you need to do is make a boot
disk with 40 track DS device descriptors, or use dmode after booting
OS-9, then do a "free /d0".  You should be able to tell how the disk is
formatted by the number of sectors reported as the capacity of the
disk.  I think (without doing the math) that 35t, DS = 630 sectors, and
40t, DS = 720 sectors.  I usually use 3.5" floppies on the CoCo,
formatted to 720k in (Nitr)OS-9, which end up being 1440 sectors.  Of
course, you do need to alter the device descriptor for those.

JCE

Andrew wrote:
> As you all know, I am doing a floppy disk conversion project for
> Carey, to rescue a bunch of data from some old floppies, and convert
> it into images which can be read under emulation. I have already
> completed the DECB subset of floppies, and I am beginning to tackle
> the OS-9 subset.
>
> However, I am running into a snag. When I worked on the DECB subset, I
> was able to determine what kind of disks the OS-9 floppy sides were
> (some of the floppies were "mixed" - one side being DECB, the other
> OS-9) by inference:
>
> Since under OS-9 there are only 35 track SSDD device descriptors and
> 40 track DSDD descriptors (but no 40 track SSDD descriptors), if there
> was readable OS-9 data on one side of a floppy and the other was DECB
> formatted (and there were two index holes punched in the floppy
> jacket), then it could only be a 35 track SSDD floppy side.
>
> However, I can't make that inference now since a 35 track SSDD floppy
> (with a single index hole) looks the same physically as a 40 track
> DSDD floppy (which also has a single index hole). Unless it is labeled
> as a certain format, I am not sure how to tell which is which.
>
> Can anyone tell me what the best way of determining whether an OS-9
> formatted floppy is a 35 track SSDD floppy or a 40 track DSDD floppy?
> Whether the method uses DECB, OS-9, or DOS, it doesn't matter.
> However, I don't have access to a Windows machine with a 5.25 floppy
> drive, so that method is out.
>
> I need to know this information so I can make a proper backup and
> recovery image of the floppy (btw - what would be the best way for me
> to create a DSK image of a 40 track DSDD OS-9 floppy under DOS?). Is
> there a way to take an image with each side using RETRIEVE.EXE and
> then combining them somehow? Or, is there something like RETRIEVE.EXE,
> that runs on DOS, that will do this?
>
> Or - could I run a program under DECB in the emulator that took each
> side image and then directly wrote it to a third image using DSKI$ and
> DSKO$? Or perhaps in a similar manner use OS-9 on the emulator to pull
> and combine each image?
>
> Hmm - this conversion effort for the OS-9 floppies has gotten hairy
> quickly. Any and all answers will be appreciated - I don't plan on
> doing anything until I have a working answer from someone(s) out
> there, or no answer is forthcoming and I have to cobble something
> together myself.
>
> Thank you in advance...
>
> -- Andrew L. Ayers
>    Glendale, Arizona
>
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