Copying Mac Disks with a Single Drive

[Scott Quinn]

> Message: 23
> Date: Thu, 8 Feb 2007 12:27:00 -0800 (PST)
> From: Fred Cisin <cisin at xenosoft.com>
> Subject: Re: Copying a Mac Disk with a Single Drive
> To: "General Discussion: On-Topic and Off-Topic Posts"
> 	<cctalk at classiccmp.org>
> Message-ID: <20070208122504.I35814 at shell.lmi.net>
> Content-Type: TEXT/PLAIN; charset=US-ASCII
>
> On Wed, 7 Feb 2007, Scott Quinn wrote:
>> with an external 400 or 800k floppy. The SuperDrive (original
>> SuperDrive, not the "new" CD/DVD one) [present on all Macs since the
>> IIx, many IIs and some SEs (SE FDHD)] has the smaller head size and
>> your older machine won't read it properly. WRT the swapping- can't
>
> There is a completely different recording method (MFM v Mac GCR).
>
> What are the dimensions of the different size heads?
>
Not sure about dimensions- the 800/400k drives I think share common 
dimensions with the PC-esque 720k drives, and the 1.4 SuperDrive is 
known to be the same dimension as the 1.44 MB PC mechanism.

It was  big issue around the time System 7 came out- if you put a 800k 
diskette in a System 7 machine with a SuperDrive the desktop file would 
be rewritten unless the disk was locked. If you then put the disk in a 
800k System 6 drive it would indicate it as corrupt (you could run it 
through Disk First Aid to get it back) because of the head sizes 
(similar to the problem with 5.25" DD floppies in the PC AT)