[Coco] Un-upgraded 3124 Multipak/Coco3 Question (fwd)

[Arthur Flexser]

Marty's thoughts on the subject....

---------- Forwarded message ----------
Date: Wed, 1 Aug 2007 18:45:45 -0700
From: martygoodman <martygoodman at sbcglobal.net>
To: Arthur Flexser <flexser at fiu.edu>
Subject: Re: [Coco] Un-upgraded 3124 Multipak/Coco3 Question (fwd)

Sheesh!  It's been so long, I forget the details of the addressing conflicts 
entailed by use a new version unupgraded Mpak with a CoCo 3!  I'll try to 
find... and refresh my memory with... some of my old articles on the 
subject.

Basically, what happens with an unupgraded Mpak and a CoCo 3  is that you 
may end up putting two sets of data on the data bus at the same time, in 
effecting outputting TO another output.  While I suppose in theory it's 
possible to cause hardware damage doing this, the more I think about this, 
from the perspective of time, this seems to me unlikely. Tho certainly a 
transitory "glitch"... including a crash...  is a much more plausible result 
of that situation.

As I recall, the upgrade for the new version Mpak has to be done using a 
small scale logic chip or two.  This because the custom logic for the 
address decoding in the new style Mpak is INSIDE a custom, inacessible, and 
no-reprogramable chip.  Unlike the case with the OLD style Mpak, where the 
address decoding for its ports was inside a PAL or GAL chip... a very 
inexpensive, generic,  and easy to program chip.

I recall working out the logic for the Mpak upgrade, compiling it into a 
fuse map for a 16V8 GAL chip, and supplying folks with such GAL chips to 
upgrade their old style Mpaks.

---marty


---marty



----- Original Message ----- 
From: "Arthur Flexser" <flexser at fiu.edu>
To: "Marty Goodman" <martygoodman at sbcglobal.net>
Sent: Wednesday, August 01, 2007 3:30 PM
Subject: [Coco] Un-upgraded 3124 Multipak/Coco3 Question (fwd)


>
>
> ---------- Forwarded message ----------
> Date: Wed, 01 Aug 2007 13:27:21 -0400
> From: David Grimmel <navydave1 at hotmail.com>
> Reply-To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> To: coco at maltedmedia.com
> Subject: [Coco] Un-upgraded 3124 Multipak/Coco3 Question
>
> I know I need to upgrade my white 3124 multi-pak to be 100% compatible 
> with
> my Coco 3, but havent gotten around to it yet. While reading a Marty 
> Goodman
> Q&A in the July 88 iss of Rainbow, he says, "even if your Coco 3 {appears}
> to work fine with your Multi-Pak, the upgrade is required. The upgrade may
> prevent slow, subtle damage to your Coco 3". I knew that using it
> un-upgraded my cause small glitches and software problems, but I didnt 
> think
> it would cause any physical permanent damage. What damage is the good DR.
> referring to? Have I already damaged my Coco 3 by using it with an
> un-upgraded 3124 multi-pak?
>
> Dave
>
>
>
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>