Re: No HDs on my //e?

[jdb8042@tamsun.tamu.edu (John Donald Baker)]

The reason High-Density floppy disks don't work in a Disk 2 (or any other
non-high-density drive) is that the Disk ][, et al. simply don't have the
necessary magnetic flux to align the domains in the HD emulsion coating.

Your standard "Double Density" disk uses a plain iron-oxide coating (like
standard-grade audio tape).  Disk ]['s and *BM-tyle 360K disk drives only
have the strength to influence this type of disk.

The high bit rate of "High Density" recording (500Kbps) requires a
"tougher" magnetic compound (harder to align) so that the data ca be
recorded reliably.  Disks intended for use the "High Density" drives
use a cobalt compound rather than simple iron oxide.  This material
requires a much higher magnetic flux to align its domains.  High density
drives are made to supply this higher field strength and have a control
line (pin 2) to tell it whether to use the higher strength or not.

Disk ]['s just don't have to power.

The same is true for 3.5" disks.  Never, ever use a HD disk in a drive
that was not made for it (original Mac drives, UniDisk 3.5's, Apple
3.5 Drive).  Further, never intentionally format a HD as DD or vice
versa.  You'll lose your data in the long run.  The disks were not
made to be formatted in a manner inconsitent with their labelling.

Here endeth the lesson.


John D. Baker  ->A TransWarp'802'd Apple //e CardZ180 Z-System nut//
Internet:  jdb8042@tamsun.tamu.edu, @blkbox.com, jdbaker@taronga.com
BBSs:  JOHN BAKER on PIC of the Mid-Town [(713) 961-5817] 1:106/31,
The Vector Board [(716) 544-1863], Z-Node #45 [(713) 937-8886]