[Coco] hardware scrolling revisited...

[fydill at aol.com]

Sent from my LG phone

"Luis Antoniosi (CoCoDemus)" <retrocanada76 at gmail.com> wrote:

>Even the NTSC "artifact colors" never existed from Tandy manuals. They
>are always said as monochrome modes. Maybe because of the PAL machines
>that are unable to handle them.
>
>But the service manual for coco2 does talk about them...
>
>
>On Mon, Dec 2, 2013 at 1:30 PM, Nick Marentes <nickma at optusnet.com.au> wrote:
>>> I think it was about late 1982 or early 1983 when the first signs of the
>>> SG-8/12/24 semi-graphics modes where no longer supported. That was when
>>> Tandy ask me to re-write Audio Spectrum Analyzer without using SG modes.
>>> (Tandy never released the non SG mode version A.S.A.) Around this time
>>> line was when Tandy stop selling 4K CoCo.
>>
>>
>> It was my understanding that semigraphics mode was not an official graphics
>> mode. It is not a mode created within the 6847 VDG but a "phantom" mode
>> created with the combination of the 6847 VDG and the SAM chip.
>>
>> In other words, without the SAM there would be no semigraphics.
>>
>> For example, the MC-10 computer has a 6847 VDG but no SAM chip and hence no
>> semigraphic mode.
>>
>> I can understand that Tandy wanted to lay the rules for software development
>> to include only the "true" modes since the SAM may not be in part of future
>> CoCo designs.
>>
>> Ironically, the CoCo3's GIME chip actually emulates the SAM and semigraphics
>> mode does still work... at least 95% of it anyway (no text).
>>
>> Nick
>>
>>
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>
>
>
>-- 
>Long live the CoCo
>
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