30 Sep
1999
30 Sep
'99
3:07 a.m.
Without beating this dead horse too much more, I'd like to add a couple of
things to the mix.
(1) I've successfully formatted DSDD diskettes to 1.2MB DSHD format. I have
also formatted DSHD diskettes to DSDD 40-track and 80-track formats, with
varying degrees of success, depending on how carefully I tracked WHERE they
had been formatted.
(2) This gives rise to at least two other points which probably need to be
stirred into the mix. (a) The drive in which the diskette was formatted
determines what kind of drive will read/write it successfully. Formatting
as DSHD must take place in a 1.2MB drive. If the lower density is to be
used successfully, care must be taken to ensure that the disketted is never
written in a DSDD drive, as the heads are different and the DSHD drive can't
erase enough of what the DSDD drive's heads have written to be completely
successful all the time. (b) WHEN the diskette was made seems to make a
great deal of difference as to whether this (item #1, above) will work, i.e.
whether the DSDD diskettes will format to DSHD with whatever massaging is
required.
Eric's comments about the emulsion placed on the media is quite correct. At
some point, however, it became economically expedient to use the same
emulsion in all of their (the diskette-makers') products as opposed to
producing two different emulsions. That led to another period during which
the bin-sorting provided a market for lots which were only slightly less
"perfect" than their standards demanded, and these were then used, together
with whatever completely adequate lots were necessary to meet the demand for
DSDD media. The "perfect" lots of stock were punched and labeled DSHD.
Clearly, a goodly portion of the time, DSDD media were sold which were
completely adequate to meet DSHD requirements.
Since the DYSAN folks in Luisville, CO, who were once a customer of mine,
practiced this in fixed disk media, I doubt it was done any differently with
floppy media . . . perhaps not, but it makes sense.
Dick
-----Original Message-----
From: Eric Smith <eric(a)brouhaha.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Thursday, September 30, 1999 4:08 AM
Subject: Re: floppy controller IC (was Re: Fixing a PET?)
Glen wrote:
> BTW my understanding is that all 5.25 diskettes made today are
bin-sorted --
that is, they
shoot for DSHD and the fallouts are sold as DSDD.
I don't believe that for an instant.
High-density requires a different, higher-coercivity coating, which will
not work properly for low density (single or double).
However, there's no difference between double density 40 track and 80 track
disks. They aren't even binned; they just get labelled differently.
30 Sep
30 Sep
3:30 a.m.
(1) I've successfully formatted DSDD diskettes to
1.2MB DSHD format. I have
also formatted DSHD diskettes to DSDD 40-track and 80-track formats, with
varying degrees of success, depending on how carefully I tracked WHERE they
had been formatted.
That tells me not to use your drives.
5.25 standard density media is 300oersted ferrite based and the correct
1.2mb media is 700o cobalt media. To write the DSHD80 to DSDD40 will work
IF... you first degauss the media then format it on the 80tr drive using
the cobalt media. It's one of those, sure but it's not reliable things.
NOTE: wrte current on both media impacts precomp and peak shift big time
considering your dealing with 2:1 changes.
Allison
Eric's comments about the emulsion placed on the
media is quite correct. At
some point, however, it became economically expedient to use the same
emulsion in all of their (the diskette-makers') products as opposed to
producing two different emulsions. That led to another period during which
This is only true for 3.5" media that is not 2.88mb and 1.2mb 5.25 as they
are distinctly different formulations. For the rest yes, all the same
stuff or very close.
allison
4:40 a.m.
New subject: Media interchange sillinesss (Was: floppy controller IC (was Re:
On Thu, 30 Sep 1999, Richard Erlacher wrote:
Without beating this dead horse too much more, I'd
like to add a couple of
things to the mix.
(1) I've successfully formatted DSDD diskettes to 1.2MB DSHD format.
This must be a new meaning of "successfully" of which I was not previously
aware. Did you store data on them? Did you read the data? Did the data
last for more than a few days? Do you CARE about the reliability of data?
I have
also formatted DSHD diskettes to DSDD 40-track and 80-track formats, with
varying degrees of success, depending on how carefully I tracked WHERE they
had been formatted.
ROYTYPE 15 years ago [apparently] mislabelled some 600 Oerstedt (1.2M)
disks and sold them for TRS-80 use. They were lots of fun! You could
format them and copy data to them "successfully"! An hour later, they
were "blank" again!
(2) This gives rise to at least two other points which
probably need to be
stirred into the mix. (a) The drive in which the diskette was formatted
determines what kind of drive will read/write it successfully. Formatting
as DSHD must take place in a 1.2MB drive. If the lower density is to be
used successfully, care must be taken to ensure that the disketted is never
written in a DSDD drive, as the heads are different and the DSHD drive can't
erase enough of what the DSDD drive's heads have written to be completely
successful all the time. (b) WHEN the diskette was made seems to make a
great deal of difference as to whether this (item #1, above) will work, i.e.
whether the DSDD diskettes will format to DSHD with whatever massaging is
required.
The 48TPI drive has tracks about every half millimeter. The track is
about a third of a millimeter wide.
96TPI has tracks about every quarter millimeter. The track is about a
sixth of a millimeter wide.
The 96TPI head can not do very good job of erasing or writing over the
wide track. Some people claim success, but _I_ want better quality than
that.
Eric's comments about the emulsion placed on the
media is quite correct. At
some point, however, it became economically expedient to use the same
emulsion in all of their (the diskette-makers') products as opposed to
producing two different emulsions. That led to another period during which
the bin-sorting provided a market for lots which were only slightly less
"perfect" than their standards demanded, and these were then used, together
with whatever completely adequate lots were necessary to meet the demand for
DSDD media. The "perfect" lots of stock were punched and labeled DSHD.
Clearly, a goodly portion of the time, DSDD media were sold which were
completely adequate to meet DSHD requirements.
I doubt it.
DD 5.25" ("360K") media is rated at 300 Oerstedt.
HD 5.25" ("1.2M") media is rated at 600 Oerstedt.
That is NOT close enough to "get away with".
BTW, in most cases, you can SEE a color difference due to the different
emuolsions.
If you can name names, do so. I have a rope, and if they have not already
been burned to the ground, ...
All of the statements about bin-sorting, and interchange of DD v HD media
are identical to the Urban Legend a while back that said that Kodak Plus-X
and Tri-X were the same, just sorted by which turned out fastest.
Surely y'all can see the parallel?
OTOH, DD ("720K") 3.5" is rated at 600 Oerstedt.
HD ( "1.4M" ) 3.5" is rated at 720 Oerstedt.
That IS close enough to "get away with", and for a while there were
people peddling special hole punches to turn perfectly good 720K diskettes
into poor quality 1.4M diskettes. I particularly liked the one that came
with instructions that talked about how they had MEASURED the diskettes
with MICROMETERS,! and KNEW that there wasn't any difference.
Since the DYSAN folks in Luisville, CO, who were once
a customer of mine,
practiced this in fixed disk media, I doubt it was done any differently with
floppy media . . . perhaps not, but it makes sense.
_I_ DOUBT IT.
Dysan did NOT ever mislabel their floppy media. What crimes they might
have committed in fixed disk media would be a different story.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
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days inactive
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