ANN: Disk2FDI 0.95a, importing CBM 1541 disks with PC floppy disk drive

From: Marko Mäkelä (
Date: 2003-11-02 15:37:32

Wolfgang Moser asked me to forward the message (originally posted to
comp.emulators.cbm) to the list.  I'm impressed, but it's a pity that
5.25" DD drives are very difficult to obtain these days.


Subject: ANN: Disk2FDI 0.95a, importing CBM 1541 disks with PC floppy 
disk drive
Date: Sun, 02 Nov 2003 01:52:14 +0100
From: Wolfgang Moser <nil@nulldevice.invalid>

Hello newsgroup,

today morning, Vincent Joguin informed me, that a new version of
his tool Disk2FDI is out. 2 years ago he developed a technique
to completely trick out the standard PC floppy disk controller,
so that some foreign disk formats (not beeing MFM or FM encoded)
can be read out with standard PC equipment.

A long time only nonstandard Amiga-MFM disks could be read out
this way, but with version 0.95a some things changed... and I
got really shocked!

Disk2FDI 0.95a now claims to import GCR encoded Commodore 1541
floppy disks with a standard IBM PC/XT/AT floppy disk
controller. But there are some requirements (hard to reach?):

  * Your PC must contain _two_ floppy disk drives both connected
    to the same floppy disk controller (USB floppy disk drives
    don't work)
  * One of the drives must be a _low_density_ 5,25" disk drive
    (360KB capacity drive)
  * The software does only work under plain DOS, probably under

Vincent told me about the 360KB low density disk drive
requirement, that these drives are rotating at only 300rpm.
High density 5,25" (1,2MB capacity) got a rotation speed of
360rpm. Because C1541 disks contain four different speed zones
Disk2FDI requires a 300rpm drive in combination with the two
bitrates of 300 and 250 KBit/s of the floppy disk controller.
Only with this setup all the four speed zones can be read out

After I got such an old drive I made some first tests. And yes,
in general it works. I was able to read out one of my 1541
disks and transfer it to a D64 disk image file.
But currently there seem to be some reliability problems. I
read out the same disk several times and compared them against
each other. With each image file 20 to 30 byte differencies
(out of 170KB) occured (only using images, that were imported
without any error messages shown up).
Take note that this problem may not be caused by Disk2FDI if
my hardware setup doesn't work properly. You all should do
independent tests for your own.

  Although some reliability problems showed up, Vincent put up
  the proof with Disk2FDI, that reading/importing Commodore GCR
  encoded disks definetly is possible with a standard PC floppy
  disk controller.

  Therefore I apologize publicly for telling people, that such
  a software method would be impossible ;-)

If you want to download and test this thing or want to read
into the very interesting tech docs, go to:


  ------ to obtain more infos about me, look up the page  ------
    ----      pwnah (at) d81 (dot) de  ----

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