[Coco] Upgraded MPIs and Harware incompatability

[Gene Heskett]

On Sunday 01 October 2006 16:55, Mark Marlette wrote:
>Bruce,
>
>OK, that is what my thinking was on my original reply to you. The
>CoCo1/2 should be fine but the 3rd party plugin hardware used
>reserved areas of the memory map and thus where broken when the CoCo3
>started using those formerly reserved areas.
>
Do you recall what 3rd party plugin might have used addresses above $FF7B?

I recall re-addressing a WP-RS, but that was to contain it within a given 4 
byte wide block instead of use 2 bytes from one block and 2 bytes from the 
next higher block. effectively locking up an 8 byte wide address space.  
The logic was available on the card, so I have NDI why it wasn't done in 
the first place, but thats another days argument.

>Thanks!!!
>
>Mark
>
>At 10/1/2006 09:59 AM, you wrote:
>>The first suggestion of a PAL switcher to switch between CoCo 3 use and
>> CoCo 1/2 use seems to be Marty Goodman in The Rainbow on January 1987
>> starting on page 98.  Here he does not say that the upgraded pack does
>> not work on CoCo 1 &2s, but rather that some 3ed party hardware will
>> not work with the upgraded MPI.  This is the earliest reference to a
>> PAL switcher I have found so far.
>>----------------------------------------------------------------------
>>In CoCo Consultations, The Rainbow, April 1987 a PAL switcher is
>> addressed. This one is a bit vague as to the reason for the need to
>> revert to the old PAL for use with the CoCo 1/2
>>------------------------------------------------------------------------
>>----
>>
>>I don't have time to research this much further now.  Suffice to say
>> there was some confusion as to the needs for the upgrade in the first
>> place, and it's affect on older equipment.
>>
>>If Mark M. states the upgraded MPIs work fine with the CoCo 1 and 2, I
>> can't argue it.
>>
>>Bruce W.
>>
>>
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>>
>>
>>
>>
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>> 9/20/2006

-- 
Cheers, Gene
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