[Coco] 3.5" floppy cable

[Kip Koon]

Hi Darren!
I've looked at the floppy connector pin out for floppy drives quite a bit.
I don't understand why swapping the "Motor Enable Drive 0" signal on pin 10
with the "Drive Select 1" signal on pin 12 will cause a floppy drive that
functions normally as drive 1 function as Drive 0.  Are the floppy
controllers for the color computer doing some non-standard (also read as
crazy) things with the floppy drives or is there another floppy pin out I'm
not aware of?  Another strange thing that happens is the standard PC floppy
cable twist of wires 10 - 16 causes a drive that functions as drive 0 or 1
to function as drive 2 or 3 respectfully on a standard DECB 1.1 unmodified
rom in tests I've performed.  I definitely was not expecting this result.
All this is quite puzzling to me.  The standard floppy connector pin out
does not lead me to believe this would ever be the case, so what are the
floppy controllers for the Cocos doing?  One more thing, why aren't the
drive selects and motor enabled signals for drives 2 & 3 shown in the floppy
drive pin outs I have looked at.  I remember in the good 'ole days of 8-bit
computing that I could jumper a drive for drive 0, 1, 2, or 3.  I have some
5.25" floppy drives with jumpers to do just that in some cases.  Now that
I'm thinking about all this, did IBM mess with the original floppy drive
signal definitions?  It seems to me there was a defined floppy drive
connector pin out standard that did include drive selects for all four
drives numbered 0, 1, 2 &3.  If so, then there are definitely two different
floppy drive connector pin outs!  Thank you in advance for helping me to
understand all this.
Kip

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Darren A
Sent: Saturday, November 09, 2013 5:41 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] 3.5" floppy cable

On Sat, Nov 9, 2013 at 1:08 PM, Bill wrote:

> I built a 3.5" drive cable, and after I put the 9-16 twist in it, the 
> drives light up when I type in DIR2 or DIR3. Is the twist for a coco 
> 3.5" floppy different than for the PC?
>
>
If you are using two drives with a CoCo, and both are configured to be Drive
1 (standard PC setting) then you need a cable with a twist of wires
10-12 only.  The drive attached after the twist will be recognized as Drive
0.

Darren

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