Re: CBM-900 floppy disk format/encoding

On 2011-10-23 01:53, MikeS wrote:
> ----- 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
>> :-)
>>

>
> 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?
>

Good questions neither the drive or the disks are in my home right now -
I propably won't be able to take a look at them before thursday evening.

I'll keep the list posted then - thank you all for your inputs so far.

>>
>>>
>>> ----- 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 :-)
>>>>





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