Re: Apple Drive III cable

[Jon O'Brien <jobrien@ais.net>]

> Okay, I've completely gutted my ///+ and my ///, as well as my disk ///
> in order to explore the posibillities I mentioned, and none work.  The
> internal drives in the /// and ///+ are identical, and upon opening up
> the disk ///, the internal mechanisms, pc board, etc. are also identical.
> From my investigations I've discovered the controller board has 2 26 pin
> dip connectors on it.  While I had wondered what the 2nd one was for
> <the first being used to connect the internal drive to the motherboard> on
> the internal drives, it became readily apparent once I opened up the disk ///.
> This second port, which is in the far back of the drive, sticks out of the
> disk /// case to provide a port to daisychain more disk ///'s to.
> However, if you plug the external disk /// into this "daisychain" port on
> the internal drive, SOS can't recognize .d2
> I wonder why this is so.  Apparently there is something on the motherboard
> level which differentiates between the "internal" drive port, and the external
> port.  I was able to hook up the external disk /// to be the boot drive
> on both my /// and my ///+ with no problems, but doing that disables the
> "daisychain" port on the drive.

I, too, cracked open my system looking for answers and also got the same results as you did.  My 
external Disk /// has a history of problems, so I wasn't sure if that was the cause of the 
problem, but your experience clears that up.

I'm curious as to how the computer can tell the difference between the internal .d1 and an 
external .d2 (or .d3 for that matter) when the ribbon cable connecting the port goes strait 
through for the internal drive.  If it is indeed a pass-through connection then the only reason 
that the port on the internal drive's analog board does not work is that it was intentionally 
disabled (i.e. jumper setting or a cut on the board).  This would make adding a 26-pin connector 
or a 26-pin -> DB25 adapter for the external drive simple.

If anyone thinks (or knows) that this is a bad idea as I naturally do not want to fry what is 
otherwise working equipment!

Jon