ProDos Disk Images

["Paul Grammens" <grammens@svn.net>]

I recently picked up a Mac 4400 with a PC Compatibility card;  it has a
133mhz Wintel PC on a card in addition to a 200 Mhz Power Mac.  I did some
experiments to see if I could create bootable ProDos disks. I knew the
manual inject floppy was not capable of making a bootable ProDos disk, but I
tried anyway. It creates the disk, and can read the disk, but the disk
wouldn't work in my IIc +.

Next I connected an auto inject floppy from an SE/30. As soon as power was
applied, the eject motor came on and stayed on. I found the pinouts for the
floppy on the two types Mac, and discovered that pin 9 has +5V on the newer
manual eject drives, but is not connected on the auto inject drives.  Pin 20
has +5V on the older drives, but is not connected on the newer ones. I
experimented with that, and found it is not necessary to supply 5V to it
because pin 11 supplies 5V.

I cut the trace on the floppy drive PC board to isolate that pin, and then
found that the drive worked normally in the 4400.  It reads, writes, and
formats properly.  So if you want to use an auto inject floppy in a Power
Mac, disconnect pin 9. The pins are labeled nicely, and I didn't want to do
any cutting on the 4400's cable, so this was the best solution for me.

However, I still couldn't make bootable ProDos floppies with the 4400.  I
reconnected the floppy to the SE/30 and verified that it could still make
bootable floppies there. I also used the same disk image on the SE/30 and
4400, just to eliminate that variable.

So the bottom line is that it seems that the floppy controller chip in this
Power Mac does not allow even a good ol' auto inject SuperDrive floppy to
make usable ProDos disks.
-Paul