Making Lisa compatible floppies

From: James MacPhail <uo957_at_email.domain.hidden>
Date: Tue, 31 Jul 2001 00:46:06 -0700

>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:

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,
uo957_at_email.domain.hidden                 but of art as engineering"
Sigma Seven Systems Ltd.
james_at_email.domain.hidden        <>

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Received on 2001-07-31 00:48:27

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