Re: DSDD vs DSHD disks

[mjmahon@aol.com (Michael J. Mahon)]

"Joel" <joelbuckley54.nospam.@hotmail.com> wrote:

> "Quadrajet1" <quadrajet1@aol.com> wrote in message
> 20021028070606.24168.00001132@mb-md.aol.com">news:20021028070606.24168.00001132@mb-md.aol.com...
> > << "Adam Barr" <omashiroi@yahoo.com> wrote in message
> > 4b54956e.0210272035.1d0531e2@posting.google.com">news:4b54956e.0210272035.1d0531e2@posting.google.com...
> > > Does any one know a place that still sells new 5.25" disks? Thanks!
> > > -Adam
> >
> >    I have a bunch of blank 5.25 disks without jackets. They are white in
>  color
> > too. Problem is, how do I tell the difference between DS/DD and DS/HD?
>  There
> > are no extra notches or markings that I am aware of, like in 3.5 disks.
> >
> >   I do run across 5.25 DS/DD disks all the time brand new in the thrift
>  stores,
> > etc all the time however.
> >
> > Raymond
> 
> I don't believe there are obvious ways to tell 360 vs 1.2M 5.25 disks.
> I don't know if this is standard or coincidence, but in looking at some of
> mine,
> the HD disk recording surface is much darker in color, blackish gray, shiny,
> while the DD is lighter, sort of brownish gray and flatter, not so shiny.
> This seems to hold up with several different brands.
> By memory, a DD disk will seldom format at HD.
> And while a HD disk will format at DD in an IBM computer, these disks can't
> be reliably read on a DD drive.
> It's not just a function of the head size and track width being smaller.
> The magnetic characteristics of the media are different.
> My memory is that HD disks did not work reliably in an Apple II.

Perhaps the easiest way is to try to format the disk in an Apple II
drive.  I have never seen an Apple II drive that could format an HD disk.

The erase & write currents that are required are twice the levels that
a Disk ][ can provide.

BTW, the coating color and the presence or absence of a hub ring
are both excellent heuristics.  Only very old non-HD disks do not
have hub rings, and no HD disks have them.

-michael

Check out 8-bit Apple sound that will amaze you on my
Home page:  http://members.aol.com/MJMahon/