[Coco] Determining OS-9 Floppy Type

[Bob Devries]

The most relaible way to determine the type of an OS9 floppy is to read LSN0 
off the disk (the first sector on side 0 track 0), and decode the first 3 
bytes as the number of sectors, the next byte (offset $04) as the number of 
sectors per track (always 18 for Coco OS9), and the byte at offset $10 (16 
decimal) of that sector, to tell you the number of sides. In OS9 parlance, 
those are called DD.TOT, DD.TKS  and DD.FMT respectively.

If *someone* can come up with a little (DOS?) routine to read that info, it 
would make life easier when trying to make disk images of OS9 disks.

--
Regards, Bob Devries, Dalby, Queensland, Australia

Isaiah 50:4 The sovereign Lord has given me
the capacity to be his spokesman,
so that I know how to help the weary.

website: http://www.home.gil.com.au/~bdevasl
my blog: http://bdevries.invigorated.org/

----- Original Message ----- 
From: "Andrew" <keeper63 at cox.net>
To: <coco at maltedmedia.com>
Sent: Sunday, May 27, 2007 12:41 PM
Subject: [Coco] Determining OS-9 Floppy Type


> 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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