30 Sep
1999
30 Sep
'99
8:17 a.m.
On Thu, 30 Sep 1999, Chuck McManis wrote:
Fascinating stuff, the old "HD/DD/SD" debate
rages even today. Fortunately
half of the conversation gets filtered on this end.
Fred's absolutely correct.
I can add only one Factoid that was true in 1986 which was that Sony and
Verbatim had both admitted that they were only made double sided diskette
media and the single sided disks were in fact double sided capable. But
_nobody_ ever claimed they used a single emulsion for both HD and DD disks.
For formats where the emulsion was the same for SD vs DD disks they did use
the same media.
Yes, SS and DS are identical.
40 track (48TPI) and 80 track (96TPI, but NOT "HD") are nominally the
same. Some people (Tony?) have had problems using "360K" diskettes for
"720K" (96TPI DD); since the specs of the media are the same, I don't know
what would be causing those problems. (always worked for me :-)
SD and DD use the same emulsion (600 Oerstedt). "HD" is a different one.
(600 Oerstedt)
Therefore, SD, DD, 40 Track, 80 track, SS, and DS could all be the same
diskette, although they would be "certified" and warranteed to different
standards.
But the "1.2M" ("HD") 5.25" diskette is a completely different
diskette.
This thread was, at one time, about 5.25" HD and DD being bin sorted. THAT
is not true. But SS, DS, SD, DD, 40, and 80 track (ALL 5.25 EXCEPT
1.2M HD) could be interchanged.
There have been STORIES that diskettes were tested, with the ones that
passed being sold as DSDD, and the ones that FAILED being retested for ss,
and maybe even removed from their jackets and flipped over to be able to
sell the "good" side as SS. Frankly, I doubt that the material costs were
ever SO high, and the labor costs SO low as to justify trying to salvage
defective diskettes.
3.5" DD and HD were NOT the same, but were close enough that you could
"get away with it" if you didn't really care about quality. (660 v 720
Oerstedt)
Richard is quite right about the need to move the index hole in the jacket
for using 8" SS as DS.
5.25" SS and DS were identical jackets.
To use the second side of a 5.25" diskette in a SS drive required punching
extra holes in the jacket. For machines such as Apple and Comm who didn't
use the index, just a new write enable notch. For machines that used the
index, such as TRS-80 and IBM, it was necessary to also punch extra holes
in the jacket for index in symmetric position. There were special jigs
available to conveniently mark the location for punching; the BEST was, of
course, the XenoSoft (formerly Berkeley Microcomputer) "Flip-Jig". (Serial
#0001 and #0002 available at VCF!)
Some people were panicy about "all of the debris" that would be released
from the lining of the diskette, but if you have that
much crap and sand,
then you had already destroyed your diskettes and drives, and
could
probably already see gouges in your diskettes.
--
Grumpy Ol' Fred cisin(a)xenosoft.com