Re: CBM-900 floppy disk format/encoding

On 2011-10-22 18:01, MikeS wrote:
> I think we're all agreed that the SFD1001 uses the same format as the 8x50,
> namely DD, GCR, 100TPI, 500KB/side, and is essentially 1/2 of an 8250.
>

Agree

> But the question is what did the CBM-900 use, and I would think it much
> more
> likely that its 1.2MB UNIX disks would be industry-compatible HD disks
> instead of somehow squeezing an extra .2MB out of a DD disk that would not
> be compatible with anything at all.
>
> So I doubt that it was actually compatible with the SFD1001, but I'm just
> guessing. In any case, if no one comes up with a definitive answer, I'd
> suggest to the OP that he try using an HD drive and diskette and see
> whether
> it works.
>

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.

Thanks for your input - I'll keep the list updates on my progress.

Since sources document that aprox 500 CBM-900 prototype units were made 
I'd have expected that this list was the (only) right place to hear 
about owners of CBM-900 systems - but it is never too late for any of 
them to speak up :-)

Thx

/Uffe


> ----- Original Message ----- From: "Greg King" <greg.king4@verizon.net>
> To: <cbm-hackers@musoftware.de>
> Sent: Saturday, October 22, 2011 5:02 AM
> Subject: Re: CBM-900 floppy disk format/encoding
>
>
>> From: "William Levak"; on Sat., October 22, 2011; at 01:11 AM -0400
>>>
>>
>>> On Fri, 21 Oct 2011, Ed Johnson wrote:
>>>
>>> > I have a SFD 1001 and it used DS/DD diskettes, NOT HD (High Density)
>>> > diskettes.
>>>
>>> The drive mechanism on the SFD 1001 is a Quad Density drive,
>>> compatible with DD, but not HD.
>>
>> "Quad" was a marketting gimmick. It wasn't related to single- and
>> double-density. It meant that the track density, not the bit density,
>> was "doubled".
>>
>> The 4040 format is 48 Tracks Per Inch, while the 8050 format is 100 TPI.
>>





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