Re: Reading 5.25" Pascal 1.3 on a Mac

[nparker@cie-2.uoregon.edu (Neil Parker)]

In article <199701020738517426609@roxboro-174.interpath.net>
phenix@interpath.com (John Moreno) writes:
>Sheldon Simms <sheldon@atlcom.net> wrote:
>] Well actually, Apple did make a PC-compatible 5.25 drive for the Mac
>] specifically for the purpose of reading MS-DOS disks, but that
>] wouldn't help your project since the PC-style 5.25 drive couldn't read
>] an Apple Pascal disk.
>
>How sure are you of this?  That's what I thought at first about the 3.5
>disk, until I tried - now it's working quite well. What's the difference
>between a disk for the Apple II and a PC disk?  I've used 5.25 disk out
>of the same box on both.  I'm not SURE that it can be done, and I would
>appreciate hearing from somebody that would be willing to try.  All they
>would need to do is email me their address and I would send them a
>diskette which they could try to read with a disk editor - FEdit, Norton
>Util. or something similar.

Physically, there's no difference between Apple 5.25-inch disks and any
other non-high-density 5.25-inch disk.  The problem is the disk controller
hardware--disk controllers have to make certain assumptions about the way
the bits are recorded as magnetic impulses.  The assumptions made by Apple
and IBM are totally incompatible with each other.

Apple's SWIM disk-controller chip (used on the Superdrive controller card
and in all recent Macs) recognizes both the Apple and PC bit-encoding
schemes, but I have no idea whether or not it's possible to hook up a
5.25-inch drive to a SWIM chip.  If it is possible, it would certainly
require special driver software to be written.

               - Neil Parker
-- 
Neil Parker, nparker@{cie-2,cie}.uoregon.edu, http://cie-2.uoregon.edu/~nparker
     "Evolution is vastly overrated."  -- Ambassador Delenn, _Babylon_5_

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