[Coco] Upgrade MPI?

[Mark Marlette]

All,
To go over what some have said about this.
It is both hardware and software based. It takes both.
As Mike has indicated, the Real Talker will cease to function on an upgraded MPI. Why?  Because they mapped the Real Talker in to a RESERVED section of the CC1/2's memory map, which just so happens to be the CC3's GIME address space,  as Robert has indicated. There could be other programs, I don't recall ATM. I at one time remapped the Real Talker and change all of the programs to use this new address.

So if you plug a non modified MPI into a CC3 and execute software that enables the conflict........anything is possible, damage to no damage can occur.
But this is for sure... it is NOT a good situation. Thus the mod put out by Tandy....they didn't do anything unless it was necessary.
My $0.02.
Regards,

Mark Marlette
http://www.cloud9tech.com
mark at cloud9tech.com
      From: K. Pruitt <pruittk at roadrunner.com>
 To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> 
 Sent: Thursday, May 7, 2015 11:46 AM
 Subject: Re: [Coco] Upgrade MPI?
   

----- 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."













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