[Coco] Multipak redesign/replacement

[Gene Heskett]

On Wednesday 25 February 2015 08:11:59 Mark Marlette wrote:
> I agree and would also like to add.....
>
> In the CC3 the address bus is unbuffered, a disaster in the works if you
> add any capacitance to the lines.

This I believe, if my 63C09 is any indication, much less of a problem in the 
63C09 case,  the 63C09 at least seems to have very robust driver outputs, 
driving solidly rail to rail at what I found was rise & fall times quite a 
few times faster than I ever saw while probing a 68B09.  Thats also fast 
enough to make a long cable ring like the liberty bell at the far end. FCC 
part 15 compliance isn't.

> From a CoCo SCSI point, most did not implement the SCSI bus properly from a
> bus drive current, termination or full SCSI ID support perspective.
>
> My experimentation in to a CC3 bus extension, left me at a reliability
> issue. Twisting, grounding, termination, shielding, etc....Wanna do it
> right and have 100% reliability, differential T/Rs....Which from a signal
> stand point = lots of parts! Real test is to xfer a hard drive and verify
> that no bit was lost. Hard to do on an extension.......YMMV.
>
> Mark Marlette
> http://www.cloud9tech.com
> mark at cloud9tech.com
> ________________________________
> From: RETRO Innovations <go4retro at go4retro.com>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Tuesday, February 24, 2015 10:23 PM
> Subject: Re: [Coco] Multipak redesign/replacement
>
> On 2/24/2015 9:33 PM, Gene Heskett wrote:
> > I can't speak to his product offering, but I am not prepared to create
> > something that causes people issues.  I appreciate that certain lengths
> > or specific brands of flat cable might do OK on 1.77MHz signals, but
> > such cable is not designed for such speeds and should not be used for
> > such speeds.
> >
> > Jim
> > Au contaire;
> >
> > Transmission line class 101 is in session:
>
> <snip>
> While I appreciate the trip down to my EE class memories, you're
> responding to a specific use case with general information.
>
> You should read the above as:
>
> ...such cable is not designed for such speeds [in the configuration Bob
> Rosen used] and should not be used...
>
> I understand SCSI, but the SCSI flat cable spec puts a ground on every
> other line, and uses terminators as you note.  Neither are present on
> Bob's cable, to my knowledge.  If they are, my apologies.
>
>
>
>
> Jim
>
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>