Apple/Mac floppy questions - test-drb@ccmp.vtda.org

2 Aug 2010

...
  Date: Mon, 02 Aug 2010 12:28:27 -0700
 From: Eric Smith <eric at brouhaha.com> 
...
  Tony wrote:
 > One thing to watch for are the little 20-way
Apple ribbon cables that
> link these drives to the mainboard. They are not what they seem -- in
> particlar 1 ro 2 wries are not wires at all, but solid plastic, so
> those
> pins of the connectors are not linked. If they are, then all sorts of
> odd
> things happen (Eject motor runs continuously???)
>
> I beelive there are at least 2 versions of the calbe (for double sided
> and high density drives>?, with different coloured pin 1 tracers. A Mac
> enthusiast may know more.
>  Jeff wrote:
  I don't remember all the details.  I do
remember that there is a cable
 with a yellow stripe on pin 1 and another version of the cable with a
 red stripe.  If you install the wrong cable (can't remember whether
 it's red for yellow or yellow for red) the eject motor does indeed run
 continuously.

 It doesn't seem to damage the drive; I never let it run more than a few
 seconds.  So it's easy enough to identify and correct.
  There's a dedicated eject signal on the 800K and FDHD that will cause
 the drive to eject.  IIRC it is active low, and replaced a ground.  The
 internal drive connectors in the Mac are not wired for that eject signal.

 The dedicated eject signal is probably used in the external drive
 enclosure for the eject button.  Software can tell the drive to disable
 the manual eject and poll the button instead.  Or something like that. 
Hmmm.  I may be remembering what happens when one tries to install an
auto-inject floppy drive into a later model Mac which expects a manual
inject drive.  In which case it has nothing to do with the cable, although
I have seen both red and yellow striped.

Anyway, I know I was building a system out of bits and pieces and saw that
behaviour from the floppy, but maybe it was auto-inject in later model Mac
rather than wrong cable.  I hadn't started keeping a lab notebook yet, at
the time.

I know I've built floppy cables for PCI PowerMacs and manual inject
floppies using standard ribbon cable and crimp on IDCs (connectors, is
that redundant with IDC?).

Jeff Walther