>However, 400KB Macintosh disks made on an early powermac did not work
>in my 1984 Macintosh. I had to use a SE/030 and even these disks crash
>the 1984 Macintosh if i try to format them.

Early Macs used a slighty revised floppy disk interface (the IWM -
Integrated Wozniak Machine) was used which was smarter at synchronizing
with the data on a floppy disk than the discrete state machine on the Lisa
I/O board.

Starting with the Mac II, the floppy disk driver software utilized this
characteristic in formatting disks.

As a result, disks made on a Mac II or later may not be readable on a Lisa
unless using MacWorks Plus II with the PFG (Programmable Frequency
Generator) that goes on the I/O board.

Later models had the SWIM (Super Wozniak Integrated Machine) and 1.4M drive
which does not have the variable speed ability of the 400/800k drives. The
controller chips modified the data rate to emulate writing to the lower
density disks. Although this works really well, I can imagine that in some
cases, this emulation may cause compatibility problems.

Hence, to make "good" 400k disks for Lisa use, I suggest you use one of the
following:

- Lisa 2
- 128k/Original Mac
- 512k Mac
- Mac Plus
- Mac SE without the superdrive upgrade

I suspect that using a 400k drive instead of an 800k drive may help give
maximum compatibility, but have not tested this.

HTH,

James

James MacPhail                   "Think not of engineering as art,
[EMAIL PROTECTED]                 but of art as engineering"
Sigma Seven Systems Ltd.
[EMAIL PROTECTED]        <http://SigmaSevenSystems.com>



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