User`s guide

specific application, it is best to stick with 35 tracks in order to retain full
compatibility with disk utilities (such as Copy II Plus) and other wares.
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002- Can I use high-density 3.5" and 5.25" diskettes on
my Apple II?
I did some magnetization tests on Double Density (800kB) and High Density
(1.4MB) diskette surfaces. The tested DD surface produced more than twice the
deflection of the tested HD surface. Clearly, there is a big difference in
signal levels required to reliably store data on HD vs. DD.
In fact, 5.25" HD (1.2MB) diskettes will not work at all on Apple Disk ][
drives. The 3.5" HD's may work fine on your 800k drives; or, they may just seem
to work fine. Either way, there's no question: a drive optimized for DD will not
be optimized for HD. If you'd rather not 'roll the dice' on your software
collection, stick with Double Density diskettes.
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From: Rubywand, George Rentovich, Mad ATARI user alternate, Joel
003- How can I tell the difference between unlabeled DD
and HD diskettes?
3.5" HD (1.4MB) diskettes come with a square notch in the upper left
corner. DD (800kB) 3.5" diskettes do not come with this notch. In the early days
of PC computing, some PC users punched or drilled notch holes in DD diskettes
and used them as HD diskettes. If a 3.5" diskette has a circular notch in the
upper left corner, it is likely to be a DD diskette.
DD 5.25" (360kB) diskettes look very much like HD 5.25" (1.2MB) diskettes;
however, HD diskettes seem to almost never have a hub ring, while DD diskettes
usually do. The hub ring may be white paper, etc. and easy to spot or cut from
the same material as the diskette and barely noticeable. This difference has
been mentioned by Peter Norton (of Norton Utilities fame) in one of his books.
The hub ring makes it easier for the Apple Disk Drive II and other older DD
5.25" drives to clamp and hold the diskette. Older DD drives also tend to damage
the center when there is no hub. If the hub ring of a DD diskette has fallen off
due to age, it's a good idea to transfer the contents to a new diskette.
Otherwise, about the only observable difference is that DD diskette
surfaces often exhibit a more brownish cast whereas HD diskette surfaces are
generally dark grey or black.
The surest test for 5.25" diskettes is to place the diskette into an Apple
Disk II 5.25" drive and try to do a DOS 3.3 format. If it formats okay, it is
almost certainly a DD diskette. (This test will not always work with the newer
40-track drives. Some of these can get through a format with an HD diskette.)