Re: Converting .DSK images to 5.25" floppy (part 2)

[mjmahon@aol.com (Michael J. Mahon)]

Charlie wrote:

>"Michael J. Mahon" <mjmahon@aol.com> wrote in message
>20031103134842.26109.00000275@mb-m16.aol.com">news:20031103134842.26109.00000275@mb-m16.aol.com...
>
>> Since my primary interest
>> was _reading_ Apple II disks, I would have been willing to re-read
>> several times to get a track read--a way of tolerating the timing
>> glitches caused by interrupts in the PC/Windows environment.
>
>If you just want to _read_ Apple II disks, you might want to try Disk2FDI (a
>shareware program by Vincent Joguin).  It allows you to read Apple II 5.25"
>disks on a PC with no unusual hardware.

Yes, I almost made a reference to his post, but was waiting for some
confirmatory experience...which you have provided.  ;-)

>I have been "playing around" with this program for a couple days and I have
>say
>that it does what I thought was impossible.  It reads a disk and saves it to
>a
>disk image in about one minute (longer if the original disk has bad sectors).
>
>You do have to re-arrange the sectors on the image to make them usable in an
>emulator but every byte of data is there.  In case you want to try it I found
>the following to work.
>
>
>Disk2fdi  should be
>sector #
>--------  ---------
>       0  0
>       D  1
>       B  2
>       9  3
>       7  4
>       5  5
>       3  6
>       1  7
>       E  8
>       C  9
>       A  A
>       8  B
>       6  C
>       4  D
>       2  E
>       F  F

This is the DOS 3.3 skew table (logical to physical sector mapping).

>A couple other things to note:
>
>You have to have two floppy disk drives on your PC (only one has to be a
>5.25").
>It won't work on Windows XP/2000/NT.
>I don't think it will work on the flip side of Apple II disks.
>You can't write to the Apple II disks with the PC.
>
>It is supposed to work for other non-PC disks as well but I haven't tried it.
>
>Here's a link:
>
>http://www.oldskool.org/disk2fdi

His technique of starting a disk read on a PC-formatted disk,
waiting for it to sync up and start to transfer data, and then
switching on the fly to the drive containing the non-PC disk
is quite novel.

Does it work with the Apple disk in a high-density 5.25" drive
and the PC disk drive a 3.5"?  (This is a fairly common drive
configuration on older machines.)

Does his program convert the nibbles to normal sectors,
or is that exercise left to the user?  (I found his documentation
rather cryptic to a non-Amiga person.)

If the PC disk controller is configured to read only from the
"bottom" surface, then flipping the disk over should work fine
(since the technique already finesses the index hole).

Many no doubt consider writing Apple II disks on a PC (which
apparently is impossible) the holy grail, but being able to read
them, however slowly, is quite handy.

-michael

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