Re: CBM-900 floppy disk format/encoding

From: MikeS <>
Date: Sat, 22 Oct 2011 12:01:09 -0400
Message-ID: <595A7D1D13C14C9CAC276D0D5886042F@vl420mt>
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.

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.


----- Original Message ----- 
From: "Greg King" <>
To: <>
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.
>       Message was sent through the cbm-hackers mailing list

       Message was sent through the cbm-hackers mailing list
Received on 2011-10-22 17:00:06

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