Re: New Dysan 5.25 double sided/double density hard case

["Michael J. Mahon" <mjmahon@aol.com>]

Martin Doherty wrote:
> mores_p@hotmail.com wrote:
>
> > Yes, i am interested. My email address is mores_p@hotmail.com. Please
> > tell me what to do.
> >
> > I assume this disks can be used with Apple 2 right? I am not an
> > experienced an apple ii user. 
> >
> > Mark
> >  
> Mark,  these are double sided, double density disks (DS-DD, 720K) and 
> the Apple II 5.25" drives are single sided, single density (SS-SD, 
> 360K).  My hunch is that they will work just fine, I bought a few boxes 
> of Verbatim DS-DD on ebay and they have been performing perfectly on my 
> Apple IIs.  However, I have heard rumours in these newsgroups that HD 
> (1.2M) disks will _not_ work well, the density is too high to work 
> reliably in the low-tech Apple drives.

5.25" SD and DD disks are identical media, differing only in the
low-level data encoding used.  Since the more advanced coding was
called "double density" all standard 5.25" disks came to be sold
as DD disks.  Their magnetic coercivity is 300 Oersteds.

5.25" HD disks are quite different, and have a coercivity of 600
Oersteds, much too high to be recordable on Apple drives.

> Double sided and single sided disks are manufactured identically, but 
> the ones labelled as single sided have only been tested on one side and 
> were usually priced a bit cheaper.

And any disk manufactured after the early 1980's will have been tested
on both sides by default.  By this time, yields were excellent, and no
truly "single sided" floppies were being made--although SS labeling
persisted for a while so that users of older systems would find what
their manuals directed them to purchase.

> A lot of Apple II users make their floppies "go further" by using a disk 
> notcher (or even a standard hole punch, if you're very careful) to turn 
> them into "flippies" and store data on both sides.  Not recommended for 
> precious data, because opposite the read head in an Apple 5.25" drive is 
> a pressure pad, so don't use this approach with your precious data, but 
> it's fine for throwing a bunch of downloaded cracked games onto it, as 
> they can be easily replaced

In fact, the pressure pad (unless missing or *very* abrasive) is less of
a threat to your "valuable data" than the opposing head of a double-
sided drive.

This myth was promulgated by "theoretical worriers" and, perhaps, by
diskette manufacturers, who would prefer to sell twice as many
diskettes.

(BTW, the only way to safely store "valuable data" is as multiple copies
stored in different places.)

> Dysan is a great brand name, very good reputation.  Other good ones are 
> Verbatim and Nashua.  Avoid the 'no-names' as the manufacturing quality 
> might not be up to par.

Again, by the mid-1980's virtually *all* diskette manufacturing was
well beyond the standards required by the very permissive Apple drives.
Major labels were already buying and labelling diskettes made in Asia,
with the result that the actual manufacturer varied from lot to lot.
(As is the case today with almost all media.)

The only real quality issue is binder longevity, and that is, sadly,
almost entirely a restrospective determination.  ;-(  We now know
that a tiny amount of fungicide/germicide might have been a wise
addition to the coating formulation for those who store diskettes
for long times in humid areas.

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."