HP Portable+ disks

[Tony Duell]

> . . . and also, disks that were used on one system and then reused on a
> different one.  The first side has a different format than the second
> side, nine sectors per track with 8 used for a different file system than
> the ninth, or a bogus MS-DOS directory left behind on track 0 and a CP/M
> directory on track 2.

Disks that have been used on a double-head drive (or have been 
factory-formatted for such a drive) which are then reformetted and used 
on a single-head drive can have some odd remnants on side 1. 

The other odd one is to have a machine that formats, say, 8 sectors per 
track, nd use a pre-formatted disk with 9 sectors per track (otheriwse 
identical format) in it. Most of the time it works fine (the machine will 
only loo kf or the first 8 sector headers). But if you come to analyse 
such a disk, you see this odd extra sector that is there for no good reason.
 
> . . .  or calling 3.5" diskettes "hard-sector"

Sinc ethe index signal in a 35." drive comes from a sensor in the motor 
(not from any kind of hole in the disk), I believe hard-sectored 3.5" 
disks are impossible., at least using the normal definiton of 'hard 
sectored'. Hard sectored 3" disks would be possible (there is an index 
hole in rthe disk and a normal LED + phototransistor sensor), but AFAIK 
no such disks were ever made. I don;t know about 3.25", etc.

> . . .  or calling 40 cylinder DSDD "Quad", and calling 80 cylinder DSDD
> "SD"!    (Superbrain)

ARGH!

What about disks with 2 different filesystems on the same side of the 
same disk? 

-tony