[Coco] Compatible RS MPIs to Coco 3

[Michael Miller]

I also wanted to add that I got a 3024 MPI late last year, and I was still able to readily get the necessary chip to upgrade it. I believe I got the chip mailed to me from Cloud9, but that may be my hazy memory... afterall I AM old enough to have had a new Coco as a young child 😊. 

http://www.frontiernet.net/~mmarlette/Cloud-9/Hardware/MPI%20PAL.html


-----Original Message-----
From: Coco <coco-bounces at maltedmedia.com> On Behalf Of Ed Snider
Sent: Saturday, December 26, 2020 11:58 AM
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Subject: Re: [Coco] Compatible RS MPIs to Coco 3

Hi Michael,

It's the 26-3024 that can be easily upgraded with the chip swap.  The chip in question is a PAL16V8 which can be replaced with a compatible chip (PAL or GAL) containing the upgraded logic.

https://www.youtube.com/watch?v=XfXG8SqXleM <https://www.youtube.com/watch?v=XfXG8SqXleM>

The new logic basically keeps the MPI from responding to the addresses added in the GIME when the CC3 was introduced (not an issue on CC1/2) to avoid bus conflicts.

- Ed


> On Dec 26, 2020, at 10:05 AM, Michael Kline via Coco <coco at maltedmedia.com> wrote:
> 
> Hi Jeff,
> 
> Thanks for the info. What chip do you swap out and are they available? Probably EPROM now-adays.
> 
> Michael
> 
> 
> 
> On 26/12/2020 09:46, Jeff Teunissen wrote:
>> No _unmodified_ Multi-Pak Interface is compatible with the CoCo 3. I 
>> believe that there was a time when Tandy took all of the 26-3124 "new"
>> MPIs they had in their warehouse and upgraded them to work with the 
>> CoCo3, resulting in 26-3124A.
>> 
>> So I guess there's one model of MPI that's CoCo3-compatible out of 
>> the box, the pretty-rare 26-3124A. All other models are incompatible 
>> unless modified. The old 26-3024 MPIs are pretty easy to upgrade, you 
>> replace one chip with another. The upgrade to the newer 26-3124 
>> version is more involved, and probably shouldn't be done unless 
>> you're pretty confident with a soldering iron.
>> 
>> On Sat, Dec 26, 2020 at 10:18 AM Michael Kline via Coco 
>> <coco at maltedmedia.com> wrote:


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