Re: Mac 400k drive on IIe?

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

In article <sbeattie.790442682@stimpy.cs.iastate.edu>,
Shawn T Beattie <sbeattie@cs.iastate.edu> wrote:
> dempson@atlantis.actrix.gen.nz (David Empson) writes:
> 
> >How is a 3.5" drive going to help, if you have no way of accessing any
> >existing software (all of which is on 5.25" disks or on 800k 3.5" disks)?
> 
> I think it might be possible to read some of the files on a 800k disk
> using a 400k drive -- the files that happen to be on side 1.  And perhaps
> you could access side 2 by popping the disk case open and flipping the
> disk over.  A file that happened to overlap both sides would have to
> be pieced together.

You'd have to be pretty lucky.  The blocks alternate between sides.
The boot sectors, directory and bitmap require 7 blocks, leaving 5
blocks on the first side of the first track.  The next 12 blocks would
be inaccessible.  The rest of the disk would alternate in 12 block
ranges (dropping one block every 16 tracks, until 8 blocks for the
last 16 tracks).

This is assuming the firmware would allow the disk to be read at all -
it might see the "double sided" flag and refuse to read it.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand