[Coco] hardware scrolling

[Steve Bjork]

John,

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.

The SG mode sure help us write those first CoCo games since all (well 
most) "Carts" in the first year had to run on 4k system.

Once the Deluxe color computer project was killed off a few years later, 
all Tandy support/use for SG 8/12/24 modes die.  It was as if it never 
existed on the CoCo.

I hope that helps.

Steve

On 12/1/2013 12:47 PM, John W. Linville wrote:
> On Sun, Dec 01, 2013 at 12:18:35AM -0800, Steve Bjork wrote:
>
>> The other problem, some of the tricks we found were not allowed to
>> be used in software we sold to Tandy,  Why?  Tandy wanted make sure
>> the old software worked on new versions of the CoCo.  As you know,
>> some software that uses semi-graphics don't work on the CoCo 3
>> because that semi-graphics mode was not supported.  Think Plug &
>> Power controller software for one.
> At what point did Tandy officially start to warn people not to use
> the SG-8/12/24 semi-graphics modes?  Obviously they aren't supported
> in the GIME, but that would come been several years later.  Was there
> any other reason for Tandy to not want people to use those modes?
>
> Some claim that those modes are 'undocumented', but they are clearly
> described in the SAM datasheet.  I'm curious to why Tandy would
> have actively discouraged use of the Color Computer's most colorful
> video modes.  Any evidence-based (i.e. not just conjecture) on the
> matter would be most welcome for some research I've been doing...
>
> John