Re: CBM-900 floppy disk format/encoding

On 2011-10-22 01:41, Ed Johnson wrote:

> Are you assuming they are not 1541 type format or do you know?

They are for a fact not 1541 type format - Kryoflux would have been able 
to get something out of the disk.

> Do you know they are Commodore High Density?
>

No I'm not sure of anything.

As stated before I've found statements about the CBM900 disk drive 
beeing SFD-1001 "like".

But I do not know if that means that the mechanical part of the drive is 
the same as the one used in SFD-1001 or if the CBM-900 contains a 
"complete" logical and mechanical SFD-1001 inside - which I find quite 
unlikely.

Also I do not know what encoding that is used for the disks - neither 
what file system.

Assuming that the resemblence with SFD-1001 is just the mechanical parts 
that are identical with SFD-1001 - CBM900 floppys does not need to use GCR.

/Uffe



> I have a SFD 1001 and it used DS/DD diskettes, NOT HD (High Density)
> diskettes.
> That was the amazing thing about it, to fit that much on a non HD diskette.
>

>
> -----Original Message-----
> From: owner-cbm-hackers@musoftware.de
> [mailto:owner-cbm-hackers@musoftware.de] On Behalf Of MikeS
> Sent: Friday, October 21, 2011 7:10 PM
> To: cbm-hackers@musoftware.de
> Subject: Re: CBM-900 floppy disk format/encoding
>
> 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.
>
> mike
>
> ----- 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
>>
>>
>>
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>
>
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>
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