Re: Did Commodore cheat with the quad density floppies?

Den Sat, 5 Jan 2019 21:38:00 +0100 skrev Rhialto <rhialto@falu.nl>:
> On Sat 05 Jan 2019 at 02:23:59 +0000, smf wrote:
> > Some people claim the labels just described how they were
> > formatted, as if people didn't know how to format them when they
> > opened the box.
> > 
> > With the plethora of different systems available that would have
> > required formatting anyway, then it seems a largely pointless
> > exercise if it's true.
> 
> I don't think I have seen pre-formatted floppies until after the
> introduction of 90mm (3 1/2 thumbs) floppies. Probably not even in
> their first years. They were always MS-DOS formatted. I always
> presumed that that was because the IBM PC compatibles had become
> popular even amongst people who didn't even know how to format a
> floppy. (If 90 mm disks had been formatted from the beginning, it
> probably would have been Apple Macintosh format)

It would be interesting to know how they wrote this to the disk.

They would need a test pattern anyway. Maybe the gap that's in those
9-sector MFM disks were used for test data?

Or maybe they used more than one head? One write head writing a test
pattern, a read head next to it checking the media quality by reading
the test pattern, and a third head writing the PC format, instead of
erasing the media which I assume otherwise would had been done. By
adding an additional head and some more electronics they got away with
a demagnetize step in the production, I assume.

But what did the heads look like? For production speed, it seems
reasonable that each head assembly contained multiple heads, one for
each track, making it possible to read/write all tracks at the same
time, resulting in testing and formatting a disk in slightly more than
one turn.
 
> (I suppose that earlier, mainframe and mini vendors like IBM and
> Digital Equipment Corporation might have sold pre-formatted floppies
> at a premium, possibly because they made it difficult for the user to
> format them themselves. Or maybe they only did that with hard disks.)

Yeah, that was imho a crappy practice :(

Btw there were also hard sector disks, with a whole lot of index holes,
one for each sector and an extra to indicate start of track. That way
they afaik didn't need to format the disks, just write the equivalent
of BAM/directory, FAT or whatever, as the sector spacing were done in
hardware and not by software.

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