[Coco] Hidden 256-color mode

[jdaggett at gate.net]

Nick

That does not make sense either. A list of address spaces with in 
the I/O address space where I have been unalbe to determine any 
peripher for the Coco 3 uses.

$FF96
$FF97
$FF9B
$FFD4
$FFD5
$FFD6
$FFD7 
$FFDA
$FFDB
$FFDC
$FFDE
also $FFE0 to $FFEF for a total of 27 registers. Another 16 could 
be at $FF80 to $FF8F. That has always made me wonder. No I/O 
peripheral use $FF80 to $FF8F. This logically is the firs block of 16 
addresses within the upper128 bytes of the memory map. Yet the 
first GIME register is at $FF90.

All would not require significant extra logic to decode these 
registers. Most likely these all are decoded already within the chip. 
So running out of registers to me seems unfounded. I still contend 
that RS dictated the cost of the GIME chip within a range and going 
over 68 pins exceeded the upper range of cost requirements. 

james


On 29 Jul 2005 at 5:53, Nickolas Marentes wrote:

Date sent:      	Fri, 29 Jul 2005 05:53:18 +1000
From:           	Nickolas Marentes 
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Subject:        	[Coco] Hidden 256-color mode
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> The "running out of pins" comment may not be totally accurate. My
> contact at Tandy who was quite high up in the chain and responsible
> for the CoCo3 (he called himself the father of the CoCo3), wasn't an
> engineer. He was more management I believe. He said "pins" but maybe
> what he meant was "registers". This makes more sense.