[Coco] What do you make of this non-approved HSCREEN mode?

[Robert Gault]

Paul Fitch wrote:
> Seems to me that in order to fully understand what is going on, you have to
> treat the mode as a "Black Box".  Ie, you give the "black Box" every
> possible input, and record every possible output.  Then once you know what
> is happening in the real world versus what the GIME documentation says
> should happen you could start to construct a model of the "real" hardware
> and compare that to the "ideal" hardware your GIME docs say you have.
> 
> I know you are asking people what they "see" when the program runs, but are
> you mapping the actual screen memory values for those bytes/pixels as well?
> There may be more going here than your eye can tell you.  If the GIME is
> writing to unanticipated areas on the screen, it could be doing it elsewhere
> as well, and not on the screen memory that you can see with your eyes.
> 

The control byte at $FF99 changes what the video circuitry shows in 
Coco3 mode. The MMU bytes control what part of memory you have actual 
access to for reading or making changes.
In light of this, care to modify what you said in your last paragraph? :)