Re: ProDos Disk Images

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

Paul Grammens wrote:

>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.

Interesting experiment.

I expect that the Power Mac controller does not provide the variable speed
control voltage that the Superdrive floppy needs.  When you format a
ProDOS (800K) disk, do you hear the drive changing speeds?

-michael

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