[Coco] MPI mod for coco3

[Bruce W. Calkins]

Upgrading 26-3024 MPIs uses a PAL/GAL chip programmed for the CoCo 3's 
addressing pattern.

Upgrading the 26-3124 involves trace cutting and wiring in a 74LS10 chip to 
change the addresses.

To make a 20-3024 MPI work with both a CoCo 1/2 and a CoCo 3 requires a 
piggybacked PAL/GAL with a switch to activate one or the other.  I'm sure 
someone can figure out some circuitry to switch the 20-3124 type MPI. 
Neither setup is stable with the other CoCos.  IE; once you upgrade to the 
CoCo 3 address set, your CoCo 1/2 will be unreliable with that MPI.

Bruce W.

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----- Original Message ----- 

From: "Luis Fernández"

> Hello friends
> I'm trying to sort cocopedia information about the modification of MPI for 
> use in coco3, and have some doubts
> There are 4 models Multipak interface
>
> Exist the Following models:
> 26-3024 Grey
> 26-3024 White
> 26-3124 White
> 26-3124A White
>
>
> The latter does not require modification (that's right?)
> The first two have the same internal circuit. and would like to revise my 
> outline, not a lot of electronics.
>
> Apparently there are two methods, one changing the PAL / GAL chip, not 
> that this is not where (or number) in the two boards
> And the other placing a 74LS10 to restrict the addresses and stuff.
> Is this true or both at once are needed?
> thanks
>