Re: CBM-900 floppy disk format/encoding

----- Original Message ----- 
From: "Uffe Jakobsen" <uffe@uffe.org>
To: <cbm-hackers@musoftware.de>
Sent: Saturday, October 22, 2011 7:22 PM
Subject: Re: CBM-900 floppy disk format/encoding


>
>
>
> On 2011-10-22 01:09, MikeS wrote:
>> Without knowing anything about the CBM-900 or even the SFD-1001 I'd say
>> it's No. 2)
>>
>>  From the specs below it looks like you should be using a 5.25" *1.2MB
>> HD* disk drive, not a DS/DD (~360KB) drive.
>>
>
> I may have written this in a way that that could be misunderstood but the 
> drive attached to my kryoflux is capable of 80 tracks (83 actually) 
> someone could argue that I should have written DS/HD than :-)
>
> /Uffe
----

Well, I can't argue what you should have written; only you can tell us 
whether you actually have a DD drive or an HD drive.

80 tracks doesn't tell us anything about the density (or the TPI for that 
matter); it could be 96TPI/DD, 100TPI/DD or 96TPI/HD.

What is the make & model of the drive?

Do the diskettes have reinforcing rings around the hub? DD diskettes usually 
do have a ring, whereas HD disks rarely do.

Also, HD diskettes are usually slightly translucent whereas DD disks are 
usually opaque; what are yours?

*******************************
>
>>
>> ----- Original Message ----- From: "Uffe Jakobsen" <uffe@uffe.org>
>> To: <cbm-hackers@musoftware.de>
>> Sent: Friday, October 21, 2011 5:51 PM
>> Subject: 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
>>>
>>>
>>>
>>> Message was sent through the cbm-hackers mailing list
>>
>>
>> Message was sent through the cbm-hackers mailing list
>
>
>
>
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