[Coco] Upgrade MPI?

[K. Pruitt]

----- Original Message ----- 
From: "Barry Nelson"
To: <coco at maltedmedia.com>
Sent: Thursday, May 07, 2015 12:53 AM
Subject: Re: [Coco] Upgrade MPI?


> It's not a software issue, it's HARDWARE. A non upgraded MPI on a CoCo 3 
> attempts to output conflicting voltage levels at the same time as the GIME 
> chip when certain registers are read. This effectively causes a short 
> circuit as one chip attempts to output 5V and the other chip tries to pull 
> the line to 0V. This happens for a very short time, but if the right 
> conditions are met, the GIME chip CAN be fried. If you care about the CoCo 
> 3 and want it to last DO NOT use an un-upgraded MPI with a CoCo 3! It can 
> fry the GIME. The is an upgrade you can apply that does not require a 
> programmed pal ship, just a single 74LS10 chip and a few wires. Here is a 
> link.
>
> http://www.coco3.com/community/2010/05/26-3124-mpi-coco-3-upgrade-1/
>
> DO NOT use it on the the CoCo3 without upgrading it! The 74LS10 chip is a 
> standard part and is readily available.
>
> FYI: I have used this upgrade on a MPI I own and in addition to working 
> correctly on the CoCo 3, I am still able to use it on my CoCo 1 as well.
>

Well, after re-reading Marty Goodman's article, and your statement above, 
I'm sufficiently frightened of the what if's.

No more using my 26-3124 with a Coco 3.  I prefer my yacht-size, and 
upgraded, 26-3024 anyway.  It keeps my Coco nice and stable on the desk.

Thanks for the link.  I had recently stated that the 26-3124A didn't need to 
be upgraded.  But I couldn't recall my source for that tidbit of info.  It's 
at the link you shared.

With the various upgrade paths available, including Cloud9, which is the 
route I went for my 26-3024, there really is no reason to risk aged hardware 
to stresses that can be easily avoided.

Even though I've used a non-upgraded 26-3124 MPI with more than one Coco 3 
without incident, I stand down from my position of "if it works it works" 
and now say "if you're gonna plug it in to a Coco 3, you should get it 
upgraded to be safe."