Re: Sales Semo on CCO

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <3id9ki$vrv@oak.oakland.edu>,
Chuck Plater <cplater@pass.wayne.edu> wrote:
>
> This happens on both our LC 475's and our Mac IIci's.  I did remember
> hearing about a problem, but I thought that it only dealt with HFS
> disks.

Randy's message rang a bell - it is mainly the 660AV and 840AV that
are affected by the problem I mentioned.  I believe it is a timing
problem - 800k disks are accessed at slightly out-of-tolerance
rotation speeds, and can have trouble reading, writing or formatting
disks that are also used on a "normal" 800k drive.

It isn't specific to HFS disks - it is a physical problem, not a
file system problem.


Anyway, it doesn't seem like this is likely to be the cause of your
problem.  The Mac IIci should definitely be OK - it has a standard
SuperDrive mechanism (unless the floppy has been replaced recently).

It may be a bug in PC Exchange, or a configuration error.  For
example, it might be formatting the disk to 720k MFM format instead of
800k GCR.  That would definitely prevent it from being read on the 800k
drive of a IIgs (it would be fine in a SuperDrive connected to a
SuperDrive card).

I think that recent Mac system software provides a special formatting
option for double density disks - "HFS Compatibility", or something
like that.  I believe this is a 720k MFM disk using HFS.  These disks
can be read in a PC with appropriate software (whereas an 800k GCR
disk cannot).
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand