Re: CBM-900 floppy disk format/encoding

From: Groepaz <>
Date: Mon, 24 Oct 2011 15:09:53 +0200
Message-Id: <>
On Sunday 23 October 2011, you wrote:
> Hi Groepaz,
> On 2011-10-23 15:18, Groepaz wrote:
> > On Sunday 23 October 2011, you wrote:
> >> Given the fact that I've already tried dumping the disks with an 80
> >> track drive (HD) - I'm leaning more to my own conclusion which is:
> >> 
> >> I need to get hold of a 100 TPI floppy drive and try that with my
> >> kryoflux.
> > 
> > i dont know what kind of analysis stuff the kryoflux tools offer - but i
> > can tell you that if it is the same format as used with the sfd1001,
> > then you should be able to read *some* tracks correctly. the lowlevel
> > encoding is the same gcr as found on 1541 (and all other cbm drives).
> > you should be able to tell which lowlevel encoding is used by making a
> > histogram of one track (again, no idea what the kryoflux tools let you
> > do).
> > 
> > and that said, 100tpi shugart drives seem to be extremely impossible to
> > find these days. i'd rather look for a solution to read those disks with
> > a PET or something :)
> I do have both SFD-1001 and CBM-8250 drives - but I doubt that the
> format used for CBM-900 floppies is the CBM GCR encoded filesystem.
> I've come to the conclusion that it is only the mechanics that is
> similar to SFD-1001.
> But I'm only guessing - later this week I'll be able to do more
> investigations on the CBM-900 story.

does the kryoflux software allow you to read a raw track and then display a 
histogram of the data? if so, try reading some of the first tracks of a disk, 
you should see either 2 (FM) or 3 (MFM/GCR) "peaks" in the histogram. if its 
the later, post the result and i can probably tell if its mfm or gcr :)


Bestaubt sind unsere Bücher, der Bierkrug macht uns klüger. Das Bier schafft 
uns Genuss, die Bücher nur Verdruss! 
<Johann Wolfgang von Goethe>

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Received on 2011-10-24 14:00:12

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