CBM-900 floppy disk format/encoding

Hi,

I'm in the progress of dumping some 5.25" disks from a CBM-900 
(protoype) system - for "obvious" preservation reasons.

The disks are labeled to contain Coherent 0.7.3 (UNIX) - (which was the 
OS for CBM-900)

 From the labels both "lowres" and "highres" Coherent disk sets exists.
I guess that has to do with hw graphics modes and not the disk format.


My problem is that I cannot read/dump the disks.

I've even tried dumping with the Kryoflux unit (http://kryoflux.com)
It does not recognise the disk either - and hence it can only produce a 
"flux" preservation dump - which it a sort of recording of the magnetic 
fluxuations on the disk surface.

The fact that Kryoflux doesn't give me anything can mean a number of things:

1) the disks are damaged - not very likely - the disks have been stored 
correct all the years.

2) the drive I'm using with kryoflux (5.25" DS/DD 83 tracks) is not the 
right type.

3) the disks are not encoded with either FM/MFM/GCR



 From various sources on the net I've read that the CBM-900 contains a 
drive that is SFD-1001 compatible and an MFM disk controller.

Quoting zimmers.net: (http://www.zimmers.net/cbmpics/c900.html)

Addition hardware:
     1.2 megabyte 5.25" disk drive (SFD-1001 compatible)
     20 megabyte hard drive
   C900 Series:    Prototype UNIX System, dropped after Amiga acquisition
                 Zilog Z8000 CPU, Runs Coherent 0.7.3, UNIX 7 clone,
                 Built-In Floppy, HD, IEEE-488. MFM Disk Controller, 1MB
           9600 bps, 500 units made. Came in two versions.

But what does the above actually mean ?

1) is it only the mechanical parts of the disk drive that is similar to 
the SFD-1001 ? or does CBM-900 contain a complete SFD-1001 with 
comtroller board etc ? (I think not)

2) The MFM disk controller ? is it for the harddisk or the floppy or both ?

Could someone give me some info on what disk format/encoding to expect 
on those Coherent disks.

Now I could take the CBM-900 apart and have a look inside - but it is 
kept in a storage room - and is unaccessible at the moment.

I'd be thankful for any information :-)

Best regards

/Uffe



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