[Coco] Multipak redesign/replacement

[RETRO Innovations]

On 2/23/2015 12:36 PM, Gene Heskett wrote:
> And I am NOT in favor of duplicating whats in the later ones as a gal, it
> is so slow at the gate buffer direction turnaround time that a truly
> serious logic short exists in mine for about 100ns as it does that.  Both
> the ground and power rails are bounced, as much as a volt, destroying the
> logic circuits noise immunity, by having both buffer directions enabled
> for a short period of overlap. That no doubt also contributes to the power
> used, and the chip temps. I do not think the 26-3024 design suffered from
> this problem, so its straight ttl logic must have been faster than the gal
> used in the 26-3124.
I'd love more detail on this.  Not sure the speed of the 14L4 in the 
3124, but I would think the 14L4 is a -20 or similar part.
>
> It is, from the image I have, apparently all one long board, rigged with a
> 40 pin cable between two IDC headers to plug it into the coco. So the
> packs are rotated 90 degrees, all still standing up so we'd see them from
> the edges.  With _good_ high resolution drawings in hand, the ones I was
> able to download aren't, this could be laid down so the carts all
> projected to the rear, getting much of the I/O cabling down out of sight a
> lot better than now.
I am dubious that the 40 pin IDC cable would work.  As I recall, that 
design was not proven to be working.  The Commodore SX64 uses a similar 
flat ribbon cable for the expansion port that sits on top of the 
machine, and it's been known for decades that the cable is the reason 
many cartridges do not work with the SX, but do with the 64
> But without locating Paul Barton, aka BartSr on some forums, so that his
> original hi res work can be obtained, this project is equally dead in the
> water.  And I do apologize to all for getting the hopes up.
Do you just want an 8 slot board design?  I was considering morphing the 
design on the PC right now into an 8 slot design, but it does contain a 
CPLD (-7ns) and uses HCT logic.

Jim


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