[Coco] Older MPI with CoCo 3

[Barry Nelson]

 It is definitely needed. The malfunctions caused without the upgrade are only a symptom or side effect of the real problem. The real problem is that an I/O port in the multipack is selected to output a signal onto the CoCo bus at the same time as a port of the GIME chip inside the color computer. This causes a momentary short circuit across the GIME chip's output. Since the duration of this short circuit is normally extremely short, usually no permanent damage occurs and you just see various minor momentary glitches. That is what normally happens. In the immortal words of Clint Eastwood:
Do you feel lucky?
Because it has the possibility of burning out the GIME chip in your CoCo 3. Of course, that chip is really easy to replace… NOT. 

On Sep 28, 2015, at 11:00 PM, coco-request at maltedmedia.com wrote:

> Date: Mon, 28 Sep 2015 20:05:07 -0500
> From: Robert Hermanek <rhermanek at centurytel.net>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Subject: Re: [Coco] Older MPI with CoCo 3
> Message-ID: <5609E3C3.6030704 at centurytel.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
> 
> Well, and perhaps someone can chime in as to whether the upgrade is 
> really "needed" or not?  As I understand it, an un-modified MPI only 
> interferes with some of the coco3's interrupt processes... but in most 
> situations, i.e. just plugging some of your favorite carts all in at 
> once, there will not necessarily be a problem.
> 
> I did not notice any issues with MPI+coco3 until I was doing some very 
> specific interrupt related ML programming.  Then I ran with my hat in my 
> hand to Cloud9 and they fixed me up :)
> 
> -RobertH