[Coco] Multipak redesign/replacement (was: Educate meaboutY-Cables)

[RETRO Innovations]

On 2/21/2015 8:52 AM, Al Hartman wrote:
> What's really needed for a first release is a multi-pak clone that 
> runs off a 5v Mini-USB power supply. It could have lights showing 
> which slot was active, and for power. I wouldn't go further than that.
>
> It could have an optional buffered cable extender so it doesn't have 
> to hang off the right side of the Coco, but could go behind it.
On that note, I spent a part of this afternoon researching this:

My first thought was 80 pin IDE cables, which might be usable (and they 
are relatively cheap and can be purchased in a circular cable format 
(essentially a flat cbale rolled up and put in a sheath, makes it look 
nicer)).  But, they only have 31 usable IO lines, and it looks like 35 
are needed (Coco has 2 ground lines, and one does not need to bring the 
+-12V and 5VDC lines over, so that's 40-5 = 35 IO lines).  IDE has 7 
ground lines, pin 20 is not used (key), and pin 34 is hacked off on an 
80 pin IDE cable. And, actually, 1 more line is needed (enable line on 
the 74ls245 data line buffer), so 36 lines are needed, and 31 are 
available.  I  went looking for SCSI cables, but not having as much luck 
there (connectors are very specialized, which means expensive).

So, the options are:

a multicable setup (80 pin IDE cable and something else to bring the 
remaining 5 IO lines over)  Maybe 2 80 pin IDE cables?
Some specialized cable that has 36 usable IO lines and a ton of ground 
lines.

And, if the first option is chosen, which 5 IO lines should be in the 
second cable (should be something buffered, so SLENB, HALT, NMI, etc. 
are probably not the best options.

Jim