[comp.os.msdos.programmer] Reading Mac diskettes on a PC

tony@cs.tamu.edu (Tony Encarnacion) (05/17/91)

Why is it that the Mac can read DOS diskettes, but the
PC cannot read Mac diskettes?  If there is a PC program
that allows a PC to do this, I'd be interested in having
it...

mike@bluemoon.uucp (Mike Cooper) (05/17/91)

tony@cs.tamu.edu (Tony Encarnacion) writes:

> Why is it that the Mac can read DOS diskettes, but the
> PC cannot read Mac diskettes?  If there is a PC program
> that allows a PC to do this, I'd be interested in having
> it...

 
Central Point's Deluxe Option Board will do the trick...


Mike Cooper | cooper@cis.ohio-state.edu | CIS:76244,3627 | Fido 
1:226/250.0

aaron@jessica.stanford.edu (Aaron Wallace) (05/17/91)

In article <16288@helios.TAMU.EDU> tony@cs.tamu.edu (Tony Encarnacion) writes:
>Why is it that the Mac can read DOS diskettes, but the
>PC cannot read Mac diskettes?  If there is a PC program
>that allows a PC to do this, I'd be interested in having
>it...

Because Apple used a non-standard encoding method, and variable speed
drives, based on the old Apple II.  At least, this is so for 400K and
800K disks.  You can read a high-density Mac disk in a high-density PC
drive just fine--well, you can read the sectors, but you'll need to make
sense of the file system on your own.

Now, why is there no product to do this?  Probably because few people
need it.  Central Point has a board that lets PCs read the 800K Mac
disks--but it's not sold too many units.

Sounds like a fun project--I was thinking of doing it myself, but I have
minimal docs on the HFS (the Mac file system) and it looks to be a terrible
hack if there ever was one!

Aaron Wallace

dahosek@biivax.dp.beckman.com (05/17/91)

In article <1991May17.154148.6341@leland.Stanford.EDU>, aaron@jessica.stanford.edu (Aaron Wallace) writes:
> Because Apple used a non-standard encoding method, and variable speed
> drives, based on the old Apple II.  

Actually, the II had straightforward 16 (or 13) soft sector
formatting on its disks. It was the Apple Lisa (do any of those
puppies still exist?) which introduced variable speed disk
drives. They had special 5.25 disks with extra notches and slots
and it sounded like it was singing when it wrote to the disk.

-dh

-- 
Don Hosek // Quixote Digital Typography   714-625-0147
     dhosek@ymir.claremont.edu
On contract to Beckman Instruments        714-961-4562
     dahosek@beckman.com

danr@bcsfse.boeing.com (Dan Richardson) (05/18/91)

Seems to me PC Magazine reviewed a product that would do just that about two or
three years ago. Rattling around my brain is the dim memory of a product called
Xenocopy, too, that would read/write a myriad of diskette formats. The last I 
heard of this company was back in 1985 or so. What I do remember is that they were
somewhere in the Silicon Valley area. Sorry I can't be of more help.

Best of luck!

----------------------------------------------------------------------------------
Dan Richardson                    | "If there's anything more important than my
Analysts International Corp.      |  ego around here, I want it caught and shot
for Boeing Computer Services      |  now!"        --Zaphod Beeblebrox
----------------------------------------------------------------------------------
"My opinions are not necessarily those of either my clients or my employers."
==================================================================================

leonard@qiclab.scn.rain.com (Leonard Erickson) (05/20/91)

dahosek@biivax.dp.beckman.com writes:

<In article <1991May17.154148.6341@leland.Stanford.EDU>, aaron@jessica.stanford.edu (Aaron Wallace) writes:
<> Because Apple used a non-standard encoding method, and variable speed
<> drives, based on the old Apple II.  

<Actually, the II had straightforward 16 (or 13) soft sector
<formatting on its disks. It was the Apple Lisa (do any of those
<puppies still exist?) which introduced variable speed disk
<drives. They had special 5.25 disks with extra notches and slots
<and it sounded like it was singing when it wrote to the disk.

The encoding on an Apple II is *not* standard from any point of view except
Apple's. The used an oddball customized circuit instead of a standard floppy
controller. Thus, the disks are unreadable on "normal" equipment.

It'salso possible to do some weird and strange things with Apple disks
because of this. This is the basis of several copy protection methods.
-- 
Leonard Erickson			leonard@qiclab.uucp
personal:	CIS: [70465,203]	70465.203@compuserve.com
business:	CIS: [76376,1107]	76376.1107@compuserve.com