Bill Garber (willy4SPAM6pa@comXcast.net) wrote:

: > A long shot, but...
: >
: > Aren't the 5.25 drives electrically similar to the Disk ][?  I know they
: > use the same interface, just with a different pin configuration...

: Electrically, yes, operationally, yes, but connectivity to the actual
: mechanism may be different, although one person has stated that
: they used a drive from an Apple 5.25 drive in a DuoDisk, which
: does make sense. I'd have to have them all open in front of me to
: be sure though.

Mechanically, I think the 5.25 and DuoDisk are identical.  It's that
godawful analog board in the DuoDisk that is whacked.  Well, if it's up to
date it should have two capacitors and a resistor whacked *off* but that
wasn't quite what I had in mind...

If I remember correctly...and I believe this is based on a David Empson
post from years ago or something like that...most of the pins in the 5.25
drive are...wait a minute, I have an old "The DOS Manual" right here...

Ah, yes.  Here it is.  On the Disk ][ controller, the relevant pins...1,
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, and 20 are all
tied together between the two connectors.  Pin 14, then, is the drive
select pin.  I remember looking at a Disk ][ controller and a DuoDisk
controller side by side once and realizing that they are identical except
for the connector...clearly the 19-pin connector has a pin designated as
Drive Select.  Daisy chaining for the 5.25 drive, then, would be simple: 
Tie all the lines on the daisy-chain port to all the lines on the drive
cable, EXCEPT, tie the drive 2 select line from the drive cable to the
drive 1 select pin on the daisy chain port.  That way a drive plugged into
the card would be Drive 1, while a drive plugged into a daisy chain port
would be Drive 2.  No electronics needed.  8-)

: > Do the newly toasted drives toast good drives?  I wonder if this is the
: > same as that chip-death you get in a Disk ][ when you don't get the
: > connector plugged in right...

: I had 2 Apple 5.25 drives on a IIc+ and one day neither one would
: write to a disk. Then I tried them individually and both worked by
: themselves. I suspect that the daisy chain circuit is the culprit. Now
: I need to try them on another machine to be sure. I do have 2 Disk II
: drives on the same machine using the "Y" adapter and they both read
: and write to anything including each other, so that sort of confirms
: that daisy chain theory.

: > --Dave Althoff, ][.
: >   Who actually prefers the Disk ][ to the 5.25 drive...

: I do actually. So far I find them more reliable and much quieter.

It was actually more of a statement than a question...but I find your
comment interesting.  More reliable, certainly...but QUIETER???!

--Dave Althoff, ][.
-- 
    /-\        _      *** Respect rides. They do not respect you. ***
   /XXX\      /X\     /X\_      _     /X\__      _     _        _____
  /XXXXX\    /XXX\  _/XXXX\_   /X\   /XXXXX\    /X\   /X\      /XXXXX
_/XXXXXXX\__/XXXXX\/XXXXXXXX\_/XXX\_/XXXXXXX\__/XXX\_/XXX\_/\_/XXXXXX