Re: High and Double density floppies

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

In article <mnementhCLyF1p.JBF@netcom.com>
mnementh@netcom.com (David R. Villegas) writes:
> dempson@swell.actrix.gen.nz (David Empson) wrote:
> >The original poster discovered that "HFS Interchange Format" disks
> >couldn't be read by the HFS FST in GS/OS, which would be true if you
> >tried to read them in the standard Apple 3.5 Drive, since it can't
> >read 720k MFM disks.
> 
> That's funny- I have an Apple 3.5 drive hooked up to my PC Transpporter
> and it reads 720k MFM disks just fine.

Oh, goody.  This subject again.

The PC Transporter can read/write 720k MFM disks in an Apple 3.5
Drive, but only if you're running it as a PC.  They cannot be accessed
from ProDOS.  The PCT/Apple 3.5 Drive combination is therefore no help
if you're trying to read an HFS disk in MFM format (unless you have
PC-based software which can read HFS disks).

The PCT pulls a few tricks to get the drive to be able to access MFM
disks, and it has a few problems.  In particular, 720k disks formatted
on the PCT are not always readable by PCs and clones.  Not everyone
has this problem, but I have run into it before.  It is also much
slower than a drive which can read MFM without help (such as the
SuperDrive, when connected to its own controller card).

The Apple 3.5 Drive cannot access MFM disks if it is connected to a
controller other than the PCT (i.e. IIgs disk port, SuperDrive card,
Universal Disk Controller, Macintosh, IIc+, etc.)


Applied Engineering also have 3.5" TransDrive.  As far as I know (I've
never seen one), it is a genuine 720k MFM mechanism, and can be used
with the PCT to access 720k disks in PC mode and from ProDOS or GS/OS.
-- 
David Empson                                                               
dempson@swell.actrix.gen.nz                                                
Snail mail: P.O. Box 27-103, Wellington, New Zealand